Journal articles: 'Carrier and Transport Proteins'

1

Wohlrab, Hartmut. "Mitochondrial Transport (Carrier) Proteins. Homodimers and Heterodimers." Biophysical Journal 96, no. 3 (February 2009): 272a—273a. http://dx.doi.org/10.1016/j.bpj.2008.12.1349.

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James Freeman, Hugh. "Trafficking of Cobalamin Transport Carrier Proteins in Celiac Disease." International Journal of Celiac Disease 10, no. 1 (September 5, 2022): 5–7. http://dx.doi.org/10.12691/ijcd-10-1-2.

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3

Bai, Xiaoyun, Trevor F. Moraes, and Reinhart A. F. Reithmeier. "Structural biology of solute carrier (SLC) membrane transport proteins." Molecular Membrane Biology 34, no. 1-2 (February 17, 2017): 1–32. http://dx.doi.org/10.1080/09687688.2018.1448123.

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Macara, Ian G. "Transport into and out of the Nucleus." Microbiology and Molecular Biology Reviews 65, no. 4 (December 1, 2001): 570–94. http://dx.doi.org/10.1128/mmbr.65.4.570-594.2001.

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SUMMARY A defining characteristic of eukaryotic cells is the possession of a nuclear envelope. Transport of macromolecules between the nuclear and cytoplasmic compartments occurs through nuclear pore complexes that span the double membrane of this envelope. The molecular basis for transport has been revealed only within the last few years. The transport mechanism lacks motors and pumps and instead operates by a process of facilitated diffusion of soluble carrier proteins, in which vectoriality is provided by compartment-specific assembly and disassembly of cargo-carrier complexes. The carriers recognize localization signals on the cargo and can bind to pore proteins. They also bind a small GTPase, Ran, whose GTP-bound form is predominantly nuclear. Ran-GTP dissociates import carriers from their cargo and promotes the assembly of export carriers with cargo. The ongoing discovery of numerous carriers, Ran-independent transport mechanisms, and cofactors highlights the complexity of the nuclear transport process. Multiple regulatory mechanisms are also being identified that control cargo-carrier interactions. Circadian rhythms, cell cycle, transcription, RNA processing, and signal transduction are all regulated at the level of nucleocytoplasmic transport. This review focuses on recent discoveries in the field, with an emphasis on the carriers and cofactors involved in transport and on possible mechanisms for movement through the nuclear pores.

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Herzig, Sébastien, Etienne Raemy, Sylvie Montessuit, Jean-Luc Veuthey, Nicola Zamboni, Benedikt Westermann, Edmund R. S. Kunji, and Jean-Claude Martinou. "Identification and Functional Expression of the Mitochondrial Pyruvate Carrier." Science 337, no. 6090 (May 24, 2012): 93–96. http://dx.doi.org/10.1126/science.1218530.

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The transport of pyruvate, the end product of glycolysis, into mitochondria is an essential process that provides the organelle with a major oxidative fuel. Although the existence of a specific mitochondrial pyruvate carrier (MPC) has been anticipated, its molecular identity remained unknown. We report that MPC is a heterocomplex formed by two members of a family of previously uncharacterized membrane proteins that are conserved from yeast to mammals. Members of the MPC family were found in the inner mitochondrial membrane, and yeast mutants lacking MPC proteins showed severe defects in mitochondrial pyruvate uptake. Coexpression of mouse MPC1 and MPC2 in Lactococcus lactis promoted transport of pyruvate across the membrane. These observations firmly establish these proteins as essential components of the MPC.

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Kunji, Edmund R. S., Martin S. King, Jonathan J. Ruprecht, and Chancievan Thangaratnarajah. "The SLC25 Carrier Family: Important Transport Proteins in Mitochondrial Physiology and Pathology." Physiology 35, no. 5 (September 1, 2020): 302–27. http://dx.doi.org/10.1152/physiol.00009.2020.

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Members of the mitochondrial carrier family (SLC25) transport a variety of compounds across the inner membrane of mitochondria. These transport steps provide building blocks for the cell and link the pathways of the mitochondrial matrix and cytosol. An increasing number of diseases and pathologies has been associated with their dysfunction. In this review, the molecular basis of these diseases is explained based on our current understanding of their transport mechanism.

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Dorwart, Michael R., Nikolay Shcheynikov, Dongki Yang, and Shmuel Muallem. "The Solute Carrier 26 Family of Proteins in Epithelial Ion Transport." Physiology 23, no. 2 (April 2008): 104–14. http://dx.doi.org/10.1152/physiol.00037.2007.

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Transepithelial Cl− and HCO3− transport is critically important for the function of all epithelia and, when altered or ablated, leads to a number of diseases, including cystic fibrosis, congenital chloride diarrhea, deafness, and hypotension ( 78 , 111 , 119 , 126 ). HCO3− is the biological buffer that maintains acid-base balance, thereby preventing metabolic and respiratory acidosis ( 48 ). HCO3− also buffers the pH of the mucosal layers that line all epithelia, protecting them from injury ( 2 ). Being a chaotropic ion, HCO3− is essential for solubilization of ions and macromolecules such as mucins and digestive enzymes in secreted fluids. Most epithelia have a Cl−/HCO3 exchange activity in the luminal membrane. The molecular nature of this activity remained a mystery for many years until the discovery of SLC26A3 and the realization that it is a member of a new family of Cl− and HCO3− transporters, the SLC26 family ( 73 , 78 ). This review will highlight structural features, the functional diversity, and several regulatory aspects of the SLC26 transporters.

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Jeschek, D., M. Steiger, D. Mattanovich, and M. Sauer. "Phospholipid vesicles to determine the transport functionality of mitochondrial carrier proteins." New Biotechnology 44 (October 2018): S113. http://dx.doi.org/10.1016/j.nbt.2018.05.1017.

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9

Wohlrab, Hartmut. "Transport proteins (carriers) of mitochondria." IUBMB Life 61, no. 1 (January 2009): 40–46. http://dx.doi.org/10.1002/iub.139.

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Galano, Melanie, Sathvika Venugopal, and Vassilios Papadopoulos. "Role of STAR and SCP2/SCPx in the Transport of Cholesterol and Other Lipids." International Journal of Molecular Sciences 23, no. 20 (October 11, 2022): 12115. http://dx.doi.org/10.3390/ijms232012115.

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Cholesterol is a lipid molecule essential for several key cellular processes including steroidogenesis. As such, the trafficking and distribution of cholesterol is tightly regulated by various pathways that include vesicular and non-vesicular mechanisms. One non-vesicular mechanism is the binding of cholesterol to cholesterol transport proteins, which facilitate the movement of cholesterol between cellular membranes. Classic examples of cholesterol transport proteins are the steroidogenic acute regulatory protein (STAR; STARD1), which facilitates cholesterol transport for acute steroidogenesis in mitochondria, and sterol carrier protein 2/sterol carrier protein-x (SCP2/SCPx), which are non-specific lipid transfer proteins involved in the transport and metabolism of many lipids including cholesterol between several cellular compartments. This review discusses the roles of STAR and SCP2/SCPx in cholesterol transport as model cholesterol transport proteins, as well as more recent findings that support the role of these proteins in the transport and/or metabolism of other lipids.

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HILDYARD, John C. W., and Andrew P. HALESTRAP. "Identification of the mitochondrial pyruvate carrier in Saccharomyces cerevisiae." Biochemical Journal 374, no. 3 (September 15, 2003): 607–11. http://dx.doi.org/10.1042/bj20030995.

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Mitochondrial pyruvate transport is fundamental for metabolism and mediated by a specific inhibitable carrier. We have identified the yeast mitochondrial pyruvate carrier by measuring inhibitor-sensitive pyruvate uptake into mitochondria from 18 different Saccharomyces cerevisiae mutants, each lacking an unattributed member of the mitochondrial carrier family (MCF). Only mitochondria from the YIL006w deletion mutant exhibited no inhibitor-sensitive pyruvate transport, but otherwise behaved normally. YIL006w encodes a 41.9 kDa MCF member with homologous proteins present in both the human and mouse genomes.

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Wang, Zhen, Wen Ding, Maosen Ruan, Yong Liu, Jing Yang, Huiqin Zhang, Bing Shen, Junfeng Wang, and Yunyan Li. "NMR and Patch-Clamp Characterization of Yeast Mitochondrial Pyruvate Carrier Complexes." Biomolecules 13, no. 5 (April 22, 2023): 719. http://dx.doi.org/10.3390/biom13050719.

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The mitochondrial pyruvate carrier (Mpc) plays an indispensable role in the transport of pyruvates across the mitochondrial inner membrane. Despite the two distinct homologous proteins, Mpc1 and Mpc2, were identified in 2012, there are still controversies on the basic functional units and oligomeric state of Mpc complexes. In this study, yeast Mpc1 and Mpc2 proteins were expressed in a prokaryotic heterologous system. Both homo- and hetero-dimers were successfully reconstituted in mixed detergents. Interactions among Mpc monomers were recorded utilizing paramagnetic relaxation enhancement (PRE) nuclear magnetic resonance (NMR) methods. By single-channel patch-clamp assays, we discovered that both the Mpc1–Mpc2 hetero-dimer and Mpc1 homo-dimer are able to transport K+ ions. Furthermore, the Mpc1–Mpc2 hetero-dimer demonstrated the ability to transport pyruvates, at a rate significantly higher than that of the Mpc1 homo-dimer, indicating that it could be the basic functional unit of Mpc complexes. Our findings provide valuable insights for further structural determination and the study of the transport mechanism of Mpc complexes.

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Ardalan, Afshan, Matthew D. Smith, and Masoud Jelokhani-Niaraki. "Uncoupling Proteins and Regulated Proton Leak in Mitochondria." International Journal of Molecular Sciences 23, no. 3 (January 28, 2022): 1528. http://dx.doi.org/10.3390/ijms23031528.

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Higher concentration of protons in the mitochondrial intermembrane space compared to the matrix results in an electrochemical potential causing the back flux of protons to the matrix. This proton transport can take place through ATP synthase complex (leading to formation of ATP) or can occur via proton transporters of the mitochondrial carrier superfamily and/or membrane lipids. Some mitochondrial proton transporters, such as uncoupling proteins (UCPs), transport protons as their general regulating function; while others are symporters or antiporters, which use the proton gradient as a driving force to co-transport other substrates across the mitochondrial inner membrane (such as phosphate carrier, a symporter; or aspartate/glutamate transporter, an antiporter). Passage (or leakage) of protons across the inner membrane to matrix from any route other than ATP synthase negatively impacts ATP synthesis. The focus of this review is on regulated proton transport by UCPs. Recent findings on the structure and function of UCPs, and the related research methodologies, are also critically reviewed. Due to structural similarity of members of the mitochondrial carrier superfamily, several of the known structural features are potentially expandable to all members. Overall, this report provides a brief, yet comprehensive, overview of the current knowledge in the field.

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14

May, J. M. "Interaction of a permeant maleimide derivative of cysteine with the erythrocyte glucose carrier. Differential labelling of an exofacial carrier thiol group and its role in the transport mechanism." Biochemical Journal 263, no. 3 (November 1, 1989): 875–81. http://dx.doi.org/10.1042/bj2630875.

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S-(Bismaleimidomethyl ether)cysteine (Cys-Mal) was synthesized as a probe for reactive thiol groups on the erythrocyte glucose carrier. Although Cys-Mal entered cells, its reaction with intracellular GSH prevented alkylation of endofacial membrane proteins, limiting its effect to the cell surface at concentrations below 5 mM. Cys-Mal irreversibly inhibited hexose transport half-maximally at 1.5 mM by decreasing the maximal rate of transport, with no effect on the affinity of substrate for the carrier. Reaction occurred with the outward-facing form of the carrier, but did not affect the ability of the carrier to change orientation. In intact cells, several exofacial proteins were labelled by [35S]Cys-Mal, including the band-4.5 glucose carrier, the labelling of which occurred on a single site sensitive to transport inhibitors. The reactive exofacial group was a thiol group, since both transport inhibition and band-4.5 labelling by Cys-Mal were abolished by the thiol-specific and impermeant compound 5,5′-dithiobis(2-nitrobenzoic acid). Selectivity for carrier labelling in cells was increased by a double differential procedure, which in turn allowed localization of the exofacial thiol group to the Mr 18,000-20,000 membrane-bound tryptic carrier fragment. In protein-depleted ghosts the exofacial thiol group was preferentially labelled at low concentrations of [35S]Cys-Mal, whereas with the reagent at 10 mM the Mr 26,000-45,000 tryptic carrier fragment was also labelled. Cys-Mal should be useful in the study of carrier thiol-group location and function.

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15

Kuan, Jeffrey, and Milton H. Saier. "The Mitochondrial Carrier Family of Transport Proteins: Structural, Functional, and Evolutionary Relationships." Critical Reviews in Biochemistry and Molecular Biology 28, no. 3 (January 1993): 209–33. http://dx.doi.org/10.3109/10409239309086795.

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16

Sluse, F. E. "Mitochondrial metabolite carrier family, topology, structure and functional properties: an overview." Acta Biochimica Polonica 43, no. 2 (June 30, 1996): 349–60. http://dx.doi.org/10.18388/abp.1996_4504.

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A set of metabolite carriers operates the traffic of numerous molecules consumed or produced in mitochondrial matrix and/or cytosolic compartments. As their existence has been predicted by the chemiosmotic theory, the first challenge, in the late sixties, was to prove their presence in the inner mitochondrial membrane and to describe the various transports carried out. The second challenge was to understand their mechanisms by the kinetic approach in intact mitochondria (seventies). The third challenge (late seventies-eighties) was to isolate and to reconstitute the carriers in liposomes in order to characterize the proteins and to establish the concept of a structural and a functional family as well as some structure-function relationship with the help of primary sequences. Genetics, molecular biology and genomic sequencing bring the fourth challenge (nineties): a raising number of putative carriers becomes known only by their primary sequences but their functions have to be discovered. The actual challenge of the future is the elucidation of the ternary structure of carrier proteins that together with site-directed mutagenesis and kinetic mechanism will permit to advance in the understanding of molecular mechanisms of transport processes.

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Arora, Deepanksha, and Daniёl Van Damme. "Motif-based endomembrane trafficking." Plant Physiology 186, no. 1 (February 19, 2021): 221–38. http://dx.doi.org/10.1093/plphys/kiab077.

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Abstract Endomembrane trafficking, which allows proteins and lipids to flow between the different endomembrane compartments, largely occurs by vesicle-mediated transport. Transmembrane proteins intended for transport are concentrated into a vesicle or carrier by undulation of a donor membrane. This is followed by vesicle scission, uncoating, and finally, fusion at the target membrane. Three major trafficking pathways operate inside eukaryotic cells: anterograde, retrograde, and endocytic. Each pathway involves a unique set of machinery and coat proteins that pack the transmembrane proteins, along with their associated lipids, into specific carriers. Adaptor and coatomer complexes are major facilitators that function in anterograde transport and in endocytosis. These complexes recognize the transmembrane cargoes destined for transport and recruit the coat proteins that help form the carriers. These complexes use either linear motifs or posttranslational modifications to recognize the cargoes, which are then packaged and delivered along the trafficking pathways. In this review, we focus on the different trafficking complexes that share a common evolutionary branch in Arabidopsis (Arabidopsis thaliana), and we discuss up-to-date knowledge about the cargo recognition motifs they use.

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Kaether, Christoph, Paul Skehel, and Carlos G. Dotti. "Axonal Membrane Proteins Are Transported in Distinct Carriers: A Two-Color Video Microscopy Study in Cultured Hippocampal Neurons." Molecular Biology of the Cell 11, no. 4 (April 2000): 1213–24. http://dx.doi.org/10.1091/mbc.11.4.1213.

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Neurons transport newly synthesized membrane proteins along axons by microtubule-mediated fast axonal transport. Membrane proteins destined for different axonal subdomains are thought to be transported in different transport carriers. To analyze this differential transport in living neurons, we tagged the amyloid precursor protein (APP) and synaptophysin (p38) with green fluorescent protein (GFP) variants. The resulting fusion proteins, APP-yellow fluorescent protein (YFP), p38-enhanced GFP, and p38-enhanced cyan fluorescent protein, were expressed in hippocampal neurons, and the cells were imaged by video microscopy. APP-YFP was transported in elongated tubules that moved extremely fast (on average 4.5 μm/s) and over long distances. In contrast, p38-enhanced GFP-transporting structures were more vesicular and moved four times slower (0.9 μm/s) and over shorter distances only. Two-color video microscopy showed that the two proteins were sorted to different carriers that moved with different characteristics along axons of doubly transfected neurons. Antisense treatment using oligonucleotides against the kinesin heavy chain slowed down the long, continuous movement of APP-YFP tubules and increased frequency of directional changes. These results demonstrate for the first time directly the sorting and transport of two axonal membrane proteins into different carriers. Moreover, the extremely fast-moving tubules represent a previously unidentified type of axonal carrier.

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Miniero, Daniela Valeria, Magnus Monné, Maria Antonietta Di Noia, Luigi Palmieri, and Ferdinando Palmieri. "Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins." International Journal of Molecular Sciences 23, no. 9 (May 2, 2022): 5060. http://dx.doi.org/10.3390/ijms23095060.

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Mitochondrial carriers, which transport metabolites, nucleotides, and cofactors across the mitochondrial inner membrane, have six transmembrane α-helices enclosing a translocation pore with a central substrate binding site whose access is controlled by a cytoplasmic and a matrix gate (M-gate). The salt bridges formed by the three PX[DE]XX[RK] motifs located on the odd-numbered transmembrane α-helices greatly contribute to closing the M-gate. We have measured the transport rates of cysteine mutants of the charged residue positions in the PX[DE]XX[RK] motifs of the bovine oxoglutarate carrier, the yeast GTP/GDP carrier, and the yeast NAD+ transporter, which all lack one of these charged residues. Most single substitutions, including those of the non-charged and unpaired charged residues, completely inactivated transport. Double mutations of charged pairs showed that all three carriers contain salt bridges non-essential for activity. Two double substitutions of these non-essential charge pairs exhibited higher transport rates than their corresponding single mutants, whereas swapping the charged residues in these positions did not increase activity. The results demonstrate that some of the residues in the charged residue positions of the PX[DE]XX[KR] motifs are important for reasons other than forming salt bridges, probably for playing specific roles related to the substrate interaction-mediated conformational changes leading to the M-gate opening/closing.

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Rehan, Mohd, Ummer R. Zargar, Ishfaq A. Sheikh, Saif A. Alharthy, Majed N. Almashjary, Adel M. Abuzenadah, and Mohd A. Beg. "Potential Disruption of Systemic Hormone Transport by Tobacco Alkaloids Using Computational Approaches." Toxics 10, no. 12 (November 26, 2022): 727. http://dx.doi.org/10.3390/toxics10120727.

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Tobacco/nicotine is one of the most toxic and addictive substances and continues to pose a significant threat to global public health. The harmful effects of smoking/nicotine affect every system in the human body. Nicotine has been associated with effects on endocrine homeostasis in humans such as the imbalance of gonadal steroid hormones, adrenal corticosteroid hormones, and thyroid hormones. The present study was conducted to characterize the structural binding interactions of nicotine and its three important metabolites, cotinine, trans-3′-hydroxycotinine, and 5′-hydroxycotinine, against circulatory hormone carrier proteins, i.e., sex-hormone-binding globulin (SHBG), corticosteroid-binding globulin (CBG), and thyroxine-binding globulin (TBG). Nicotine and its metabolites formed nonbonded contacts and/or hydrogen bonds with amino acid residues of the carrier proteins. For SHBG, Phe-67 and Met-139 were the most important amino acid residues for nicotine ligand binding showing the maximum number of interactions and maximum loss in ASA. For CBG, Trp-371 and Asn-264 were the most important amino acid residues, and for TBG, Ser-23, Leu-269, Lys-270, Asn-273, and Arg-381 were the most important amino acid residues. Most of the amino acid residues of carrier proteins interacting with nicotine ligands showed a commonality with the interacting residues for the native ligands of the proteins. Taken together, the results suggested that nicotine and its three metabolites competed with native ligands for binding to their carrier proteins. Thus, nicotine and its three metabolites may potentially interfere with the binding of testosterone, estradiol, cortisol, progesterone, thyroxine, and triiodothyronine to their carrier proteins and result in the disbalance of their transport and homeostasis in the blood circulation.

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Simpson, Jeremy C., Tommy Nilsson, and Rainer Pepperkok. "Biogenesis of Tubular ER-to-Golgi Transport Intermediates." Molecular Biology of the Cell 17, no. 2 (February 2006): 723–37. http://dx.doi.org/10.1091/mbc.e05-06-0580.

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Tubular transport intermediates (TTIs) have been described as one class of transport carriers in endoplasmic reticulum (ER)-to-Golgi transport. In contrast to vesicle budding and fusion, little is known about the molecular regulation of TTI synthesis, transport and fusion with target membranes. Here we have used in vivo imaging of various kinds of GFP-tagged proteins to start to address these questions. We demonstrate that under steady-state conditions TTIs represent ∼20% of all moving transport carriers. They increase in number and length when more transport cargo becomes available at the donor membrane, which we induced by either temperature-related transport blocks or increased expression of the respective GFP-tagged transport markers. The formation and motility of TTIs is strongly dependent on the presence of intact microtubules. Microinjection of GTPγS increases the frequency of TTI synthesis and the length of these carriers. When Rab proteins are removed from membranes by microinjection of recombinant Rab-GDI, the synthesis of TTIs is completely blocked. Microinjection of the cytoplasmic tails of the p23 and p24 membrane proteins also abolishes formation of p24-containing TTIs. Our data suggest that TTIs are ER-to-Golgi transport intermediates that form preferentially when transport-competent cargo exists in excess at the donor membrane. We propose a model where the interaction of the cytoplasmic tails of membrane proteins with microtubules are key determinants for TTI synthesis and may also serve as a so far unappreciated model for aspects of transport carrier formation.

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Monné, Magnus, Alan J. Robinson, Christoph Boes, Michael E. Harbour, Ian M. Fearnley, and Edmund R. S. Kunji. "The Mimivirus Genome Encodes a Mitochondrial Carrier That Transports dATP and dTTP." Journal of Virology 81, no. 7 (January 17, 2007): 3181–86. http://dx.doi.org/10.1128/jvi.02386-06.

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ABSTRACT Members of the mitochondrial carrier family have been reported in eukaryotes only, where they transport metabolites and cofactors across the mitochondrial inner membrane to link the metabolic pathways of the cytosol and the matrix. The genome of the giant virus Mimiviridae mimivirus encodes a member of the mitochondrial carrier family of transport proteins. This viral protein has been expressed in Lactococcus lactis and is shown to transport dATP and dTTP. As the 1.2-Mb double-stranded DNA mimivirus genome is rich in A and T residues, we speculate that the virus is using this protein to target the host mitochondria as a source of deoxynucleotides for its replication.

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Hedrich, Rainer, Norbert Sauer, and H. Ekkehard Neuhaus. "Sugar transport across the plant vacuolar membrane: nature and regulation of carrier proteins." Current Opinion in Plant Biology 25 (June 2015): 63–70. http://dx.doi.org/10.1016/j.pbi.2015.04.008.

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Anderson, Catriona M. H., and David T. Thwaites. "Hijacking Solute Carriers for Proton-Coupled Drug Transport." Physiology 25, no. 6 (December 2010): 364–77. http://dx.doi.org/10.1152/physiol.00027.2010.

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The physiological role of mammalian solute carrier (SLC) proteins is to mediate transmembrane movement of electrolytes, nutrients, micronutrients, vitamins, and endogenous metabolites from one cellular compartment to another. Many transporters in the small intestine, kidney, and solid tumors are H+-coupled, driven by local H+-electrochemical gradients, and transport numerous drugs. These transporters include PepT1 and PepT2 (SLC15A1/2), PCFT (SLC46A1), PAT1 (SLC36A1), OAT10 (SLC22A13), OATP2B1 (SLCO2B1), MCT1 (SLC16A1), and MATE1 and MATE2-K (SLC47A1/2).

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Stange, J., and S. Mitzner. "A Carrier-Mediated Transport of Toxins in a Hybrid Membrane. Safety Barrier between a Patients Blood and a Bioartificial Liver." International Journal of Artificial Organs 19, no. 11 (November 1996): 677–91. http://dx.doi.org/10.1177/039139889601901109.

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Combination of detoxifying liver support systems with liver cell bioreactors may have additional benefits for the treatment of liver failure due to the replacement of known and unknown metabolic activities of the liver. However, the problem of side effects and possible risks caused by the use of animal hepatocytes or hepatoma cells remains unsolved which underlines the need of a safety barrier between the patients blood and the extracorporeal bioreactor. Passive filters do not meet the requirements of such membranes, because in liver failure desired and undesired molecules in the patients blood share similar physicochemical properties. That challanges the developement of biologically designed separation membranes. A hybrid membrane is formed by implementation of transport proteins into a highly permeable hollow fiber. The transport of free solutes and albumin bound toxins is tested in vitro in comparison with conventional high flux membranes. The transport characteristics for tightly albumin bound toxins are significantly improved for the hybrid membrane. The transport of albumin bound toxins across the membrane is not associated with albumin. The selectivity of the transport is evaluated in vivo. No significant loss of middle molecular weight hormones attached to other carrier proteins was observed. Neither transport of immunologically relevant proteins across the membrane nor loss of valuable proteins was measured. Also in vivo, a significant reduction of protein bound toxins and a transport of metabolically relevant solutes, like amino acids, was shown. The presented hybrid membrane may be used like an “intellegent membrane” as a safety barrier between the patients blood and cell devices.

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Palmieri, Ferdinando, and Ciro Leonardo Pierri. "Mitochondrial metabolite transport." Essays in Biochemistry 47 (June 14, 2010): 37–52. http://dx.doi.org/10.1042/bse0470037.

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The flux of a variety of metabolites, nucleotides and coenzymes across the inner membrane of mitochondria is catalysed by a nuclear-coded superfamily of secondary transport proteins called MCs (mitochondrial carriers). The importance of MCs is demonstrated by their wide distribution in all eukaryotes, their role in numerous metabolic pathways and cell functions, and the identification of several diseases caused by alterations of their genes. MCs can easily be recognized in databases thanks to their striking sequence features. Until now, 22 MC subfamilies, which are well conserved throughout evolution, have been functionally characterized, mainly by transport assays upon heterologous gene expression, purification and reconstitution into liposomes. Given the significant sequence conservation, it is thought that all MCs use the same basic transport mechanism, although they exhibit different modes of transport and driving forces and their substrates vary in nature and size. Based on substrate specificity, sequence conservation and carrier homology models, progress has recently been made in understanding the transport mechanism of MCs by new insights concerning the existence of a substrate-binding site in the carrier cavity, of cytosolic and matrix gates and conserved proline and glycine residues in each of the six transmembrane α-helices. These structural properties are believed to play an important role in the conformational changes required for substrate translocation.

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Pasquadibisceglie, Andrea, and Fabio Polticelli. "Computational studies of the mitochondrial carrier family SLC25. Present status and future perspectives." Bio-Algorithms and Med-Systems 17, no. 2 (April 27, 2021): 65–78. http://dx.doi.org/10.1515/bams-2021-0018.

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Abstract The members of the mitochondrial carrier family, also known as solute carrier family 25 (SLC25), are transmembrane proteins involved in the translocation of a plethora of small molecules between the mitochondrial intermembrane space and the matrix. These transporters are characterized by three homologous domains structure and a transport mechanism that involves the transition between different conformations. Mutations in regions critical for these transporters’ function often cause several diseases, given the crucial role of these proteins in the mitochondrial homeostasis. Experimental studies can be problematic in the case of membrane proteins, in particular concerning the characterization of the structure–function relationships. For this reason, computational methods are often applied in order to develop new hypotheses or to support/explain experimental evidence. Here the computational analyses carried out on the SLC25 members are reviewed, describing the main techniques used and the outcome in terms of improved knowledge of the transport mechanism. Potential future applications on this protein family of more recent and advanced in silico methods are also suggested.

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Saftner, Robert A. "STRUCTURAL DETERMINANTS REQUIRED FOR IDENTIFICATION OF ACC TRANSPORT-RELATED MEMBRANE PROTEINS." HortScience 30, no. 2 (April 1995): 190c—190. http://dx.doi.org/10.21273/hortsci.30.2.190c.

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The ethylene precursor, 1 -aminocyclopropane- 1 -carboxylic acid (ACC), is actively transported across the tonoplast of plant cells, impacting cellular compartmentation of ACC and ethylene biosynthesis. To identify potential photoaffinity probes for identifying ACC transport-related membrane proteins, the effects of over 70 ACC and other amino acid analogs on ACC uptake into isolated maize vacuoles were investigated. Only relatively nonpolar, neutral amino acid stereoisomers of L-configuration were strong inhibitors of ACC transport. Group additions, substitutions, or deletions at the carboxyl, (x-amino and the Pro-(R) methylene, or hydrogen moieties essentially eliminated transport inhibition, whereas side-chain substitutions remained antagonistic. The kinetics of ACC and neutral L-amino acid analogs tested were competitive. The results indicate that the ACC transport system can be classified as a neutral L-amino acid carrier having a relatively high affinity for ACC and other nonpolar amino acids. The results also suggest that the carrier interacts with the carboxyl, alpha-amino, and Pro-(R) groups and the side chain of substrate amino acids. Based on these findings, potential photoaffinity probes of the ACC transport system have been identified.

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INDIVERI, Cesare, Vito IACOBAZZI, Nicola GIANGREGORIO, and Ferdinando PALMIERI. "The mitochondrial carnitine carrier protein: cDNA cloning, primary structure and comparison with other mitochondrial transport proteins." Biochemical Journal 321, no. 3 (February 1, 1997): 713–19. http://dx.doi.org/10.1042/bj3210713.

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The amino acid sequence of the rat carnitine carrier protein, a component of the inner membranes of mitochondria, has been deduced from the sequences of overlapping cDNA clones. These clones were generated in polymerase chain reactions with primers and probes based on amino acid sequence information, obtained from the direct sequencing of internal peptides of the purified carnitine carrier protein from rat. The protein sequence of the carrier, including the initiator methionine, has a length of 301 amino acids. The mature protein has a modified α-amino group, although the nature of this modification and the precise position of the N-terminal residue have not been ascertained. Analysis of the carnitine carrier sequence shows that the protein contains a 3-fold repeated sequence about 100 amino acids in length. Dot plot comparisons and sequence alignment demonstrate that these repeated domains are related to each other and also to the repeats of similar length that are present in the other mitochondrial carrier proteins sequenced so far. The hydropathy analysis of the carnitine carrier supports the view that the domains are folded into similar structural motifs, consisting of two transmembrane α-helices joined by an extensive extramembranous hydrophilic region. Southern blotting experiments suggest that both the human and the rat genomes contain single genes for the carnitine carrier. These studies provide the primary structure of the mitochondrial carnitine carrier protein and allow us to identify this metabolically important transporter as a member of the mitochondrial carrier family, and the sixth of the members whose biochemical function has already been identified.

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Palmieri, Ferdinando, Pasquale Scarcia, and Magnus Monné. "Diseases Caused by Mutations in Mitochondrial Carrier Genes SLC25: A Review." Biomolecules 10, no. 4 (April 23, 2020): 655. http://dx.doi.org/10.3390/biom10040655.

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In the 1980s, after the mitochondrial DNA (mtDNA) had been sequenced, several diseases resulting from mtDNA mutations emerged. Later, numerous disorders caused by mutations in the nuclear genes encoding mitochondrial proteins were found. A group of these diseases are due to defects of mitochondrial carriers, a family of proteins named solute carrier family 25 (SLC25), that transport a variety of solutes such as the reagents of ATP synthase (ATP, ADP, and phosphate), tricarboxylic acid cycle intermediates, cofactors, amino acids, and carnitine esters of fatty acids. The disease-causing mutations disclosed in mitochondrial carriers range from point mutations, which are often localized in the substrate translocation pore of the carrier, to large deletions and insertions. The biochemical consequences of deficient transport are the compartmentalized accumulation of the substrates and dysfunctional mitochondrial and cellular metabolism, which frequently develop into various forms of myopathy, encephalopathy, or neuropathy. Examples of diseases, due to mitochondrial carrier mutations are: combined D-2- and L-2-hydroxyglutaric aciduria, carnitine-acylcarnitine carrier deficiency, hyperornithinemia-hyperammonemia-homocitrillinuria (HHH) syndrome, early infantile epileptic encephalopathy type 3, Amish microcephaly, aspartate/glutamate isoform 1 deficiency, congenital sideroblastic anemia, Fontaine progeroid syndrome, and citrullinemia type II. Here, we review all the mitochondrial carrier-related diseases known until now, focusing on the connections between the molecular basis, altered metabolism, and phenotypes of these inherited disorders.

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Kramer, R. "Mitochondrial carrier proteins can reversibly change their transport mode: the cases of the aspartate/glutamate and the phosphate carrier." Experimental Physiology 83, no. 2 (March 1, 1998): 259–65. http://dx.doi.org/10.1113/expphysiol.1998.sp004111.

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Hoppins, Suzanne, Jennifer Horner, Cheng Song, J. Michael McCaffery, and Jodi Nunnari. "Mitochondrial outer and inner membrane fusion requires a modified carrier protein." Journal of Cell Biology 184, no. 4 (February 23, 2009): 569–81. http://dx.doi.org/10.1083/jcb.200809099.

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In yeast, three proteins are essential for mitochondrial fusion. Fzo1 and Mgm1 are conserved guanosine triphosphatases that reside in the outer and inner membranes, respectively. At each membrane, these conserved proteins are required for the distinct steps of membrane tethering and lipid mixing. The third essential component is Ugo1, an outer membrane protein in the mitochondrial transport protein family. We show that Ugo1 is a modified member of this family, containing three transmembrane domains and existing as a dimer, a structure that is critical for the fusion function of Ugo1. Our functional analysis of Ugo1 indicates that it is required distinctly for both outer and inner membrane fusion after membrane tethering, indicating that it operates at the lipid-mixing step of fusion. This role is distinct from the fusion dynamin-related proteins and thus demonstrates that at each membrane, a single fusion protein is not sufficient to drive the lipid-mixing step, but instead, this step requires a more complex assembly of proteins.

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Wright, E. M., D. D. Loo, M. Panayotova-Heiermann, M. P. Lostao, B. H. Hirayama, B. Mackenzie, K. Boorer, and G. Zampighi. "'Active' sugar transport in eukaryotes." Journal of Experimental Biology 196, no. 1 (November 1, 1994): 197–212. http://dx.doi.org/10.1242/jeb.196.1.197.

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Sugar transporters in prokaryotes and eukaryotes belong to a large family of membrane proteins containing 12 transmembrane alpha-helices. They are divided into two classes: one facilitative (uniporters) and the other concentrative (cotransporters or symporters). The concentrative transporters are energised by either H+ or Na+ gradients, which are generated and maintained by ion pumps. The facilitative and H(+)-driven sugar transporters belong to a gene family with a distinctive secondary structure profile. The Na(+)-driven transporters belong to a separate, small gene family with no homology at either the primary or secondary structural levels. It is likely that the Na(+)- and H(+)-driven sugar cotransporters share common transport mechanisms. To explore these mechanisms, we have expressed cloned eukaryote Na+/sugar cotransporters (SGLT) in Xenopus laevis oocytes and measured the kinetics of sugar transport using two-electrode voltage-clamp techniques. For SGLT1, we have developed a six-state ordered model that accounts for the experimental data. To test the model we have carried out the following experiments. (i) We measured pre-steady-state kinetics of SGLT1 using voltage-jump techniques. In the absence of sugar, SGLT1 exhibits transient carrier currents that reflect voltage-dependent conformational changes of the protein. Time constants for the carrier currents give estimates of rate constants for the conformational changes, and the charge movements, integrals of the transient currents, give estimates of the number and valence of SGLT1 proteins in the plasma membrane. Ultrastructural studies have confirmed these estimates of SGLT1 density. (ii) We have perturbed the kinetics of the cotransporter by site-directed mutagenesis of selected residues.(ABSTRACT TRUNCATED AT 250 WORDS)

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Endo, Toshiya, and Haruka Sakaue. "Multifaceted roles of porin in mitochondrial protein and lipid transport." Biochemical Society Transactions 47, no. 5 (October 31, 2019): 1269–77. http://dx.doi.org/10.1042/bst20190153.

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Abstract Mitochondria are essential eukaryotic organelles responsible for primary cellular energy production. Biogenesis, maintenance, and functions of mitochondria require correct assembly of resident proteins and lipids, which require their transport into and within mitochondria. Mitochondrial normal functions also require an exchange of small metabolites between the cytosol and mitochondria, which is primarily mediated by a metabolite channel of the outer membrane (OM) called porin or voltage-dependent anion channel. Here, we describe recently revealed novel roles of porin in the mitochondrial protein and lipid transport. First, porin regulates the formation of the mitochondrial protein import gate in the OM, the translocase of the outer membrane (TOM) complex, and its dynamic exchange between the major form of a trimer and the minor form of a dimer. The TOM complex dimer lacks a core subunit Tom22 and mediates the import of a subset of mitochondrial proteins while the TOM complex trimer facilitates the import of most other mitochondrial proteins. Second, porin interacts with both a translocating inner membrane (IM) protein like a carrier protein accumulated at the small TIM chaperones in the intermembrane space and the TIM22 complex, a downstream translocator in the IM for the carrier protein import. Porin thereby facilitates the efficient transfer of carrier proteins to the IM during their import. Third, porin facilitates the transfer of lipids between the OM and IM and promotes a back-up pathway for the cardiolipin synthesis in mitochondria. Thus, porin has roles more than the metabolite transport in the protein and lipid transport into and within mitochondria, which is likely conserved from yeast to human.

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Zara, V., K. Dietmeier, A. Palmisano, A. Vozza, J. Rassow, F. Palmieri, and N. Pfanner. "Yeast mitochondria lacking the phosphate carrier/p32 are blocked in phosphate transport but can import preproteins after regeneration of a membrane potential." Molecular and Cellular Biology 16, no. 11 (November 1996): 6524–31. http://dx.doi.org/10.1128/mcb.16.11.6524.

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Two different functions have been proposed for the phosphate carrier protein/p32 of Saccharomyces cerevisiae mitochondria: transport of phosphate and requirement for import of precursor proteins into mitochondria. We characterized a yeast mutant lacking the gene for the phosphate carrier/p32 and found both a block in the import of phosphate and a strong reduction in the import of preproteins transported to the mitochondrial inner membrane and matrix. Binding of preproteins to the surface of mutant mitochondria and import of outer membrane proteins were not inhibited, indicating that the inhibition of protein import occurred after the recognition step at the outer membrane. The membrane potential across the inner membrane of the mutant mitochondria was strongly reduced. Restoration of the membrane potential restored preprotein import but did not affect the block of phosphate transport of the mutant mitochondria. We conclude that the inhibition of protein import into mitochondria lacking the phosphate carrier/p32 is indirectly caused by a reduction of the mitochondrial membrane potential (delta(gamma)), and we propose a model that the reduction of delta(psi) is due to the defective phosphate import, suggesting that phosphate transport is the primary function of the phosphate carrier/p32.

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Obermaier-Kusser, B., C. Mühlbacher, J. Mushack, E. Rattenhuber, M. Fehlmann, and H. U. Haring. "Regulation of glucose carrier activity by AlCl3 and phospholipase C in fat-cells." Biochemical Journal 256, no. 2 (December 1, 1988): 515–20. http://dx.doi.org/10.1042/bj2560515.

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Recently it was speculated that activation of GTP-binding proteins and of phospholipase is involved in the transmission of a signal from the insulin-receptor kinase to effector systems in the cell. To confirm this hypothesis, we have tested the effect of AlCl3, which has been recently used as an experimental tool to activate GTP-binding proteins, on glucose transport in fat-cells. We found that AlCl3 has a partial insulin-like effect on glucose transport activity (3-O-methylglucose uptake, expressed as % of equilibrium value per 4 s: basal 9.6 +/- 2, AlCl3 29.6 +/- 4, insulin 74.0 +/- 3). The AlCl3 effect is totally blocked by pertussis toxin, whereas the insulin effect was not altered. The effect starts at [AlCl3] greater than 1 fM and reaches its maximum at 0.1 nM. Addition of phospholipase C (PLC; 50 munits/ml) also stimulated glucose transport (maximal 53.0 +/- 5%). Both substances acted faster than insulin itself (maximal values within 1 min for PLC, 2 min for AlCl3 and 5-10 min for insulin). Using the cytochalasin-B-binding assay to determine the effects of AlCl3 and PLC on the distribution of glucose carrier sites in subcellular fractions, we found that their glucose-transport-stimulating effect does not occur through an increase in glucose carrier sites in the plasma-membrane fraction. When PLC was combined with the phorbol ester TPA (12-O-tetradecanoylphorbol 13-acetate), which increases glucose carrier sites in the plasma membrane, an additive effect on glucose transport was found [PLC (50 munits/ml), 53.0 +/- 5%, TPA (1 nM), 17.3 +/- 2%; PLC + TPA, 68.0 +/- 3%]. In conclusion: (1) the data show that AlCl3, probably through activation of a pertussis-toxin-inhibitable G protein, and PLC are able to modulate the intrinsic glucose carrier activity; (2) as pertussis toxin did not modify the effect of insulin, it seems unlikely that the insulin signal on glucose transport involves activation of this specific G protein.

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King, Martin S., Sotiria Tavoulari, Vasiliki Mavridou, Alannah C. King, John Mifsud, and Edmund R. S. Kunji. "A Single Cysteine Residue in the Translocation Pathway of the Mitosomal ADP/ATP Carrier from Cryptosporidium parvum Confers a Broad Nucleotide Specificity." International Journal of Molecular Sciences 21, no. 23 (November 26, 2020): 8971. http://dx.doi.org/10.3390/ijms21238971.

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Cryptosporidiumparvum is a clinically important eukaryotic parasite that causes the disease cryptosporidiosis, which manifests with gastroenteritis-like symptoms. The protist has mitosomes, which are organelles of mitochondrial origin that have only been partially characterized. The genome encodes a highly reduced set of transport proteins of the SLC25 mitochondrial carrier family of unknown function. Here, we have studied the transport properties of one member of the C. parvum carrier family, demonstrating that it resembles the mitochondrial ADP/ATP carrier of eukaryotes. However, this carrier has a broader substrate specificity for nucleotides, transporting adenosine, thymidine, and uridine di- and triphosphates in contrast to its mitochondrial orthologues, which have a strict substrate specificity for ADP and ATP. Inspection of the putative translocation pathway highlights a cysteine residue, which is a serine in mitochondrial ADP/ATP carriers. When the serine residue is replaced by cysteine or larger hydrophobic residues in the yeast mitochondrial ADP/ATP carrier, the substrate specificity becomes broad, showing that this residue is important for nucleotide base selectivity in ADP/ATP carriers.

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Allen, C. Leigh, and Andrew M. Gulick. "Structural and bioinformatic characterization of anAcinetobacter baumanniitype II carrier protein." Acta Crystallographica Section D Biological Crystallography 70, no. 6 (May 30, 2014): 1718–25. http://dx.doi.org/10.1107/s1399004714008311.

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Microorganisms produce a variety of natural productsviasecondary metabolic biosynthetic pathways. Two of these types of synthetic systems, the nonribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs), use large modular enzymes containing multiple catalytic domains in a single protein. These multidomain enzymes use an integrated carrier protein domain to transport the growing, covalently bound natural product to the neighboring catalytic domains for each step in the synthesis. Interestingly, some PKS and NRPS clusters contain free-standing domains that interact intermolecularly with other proteins. Being expressed outside the architecture of a multi-domain protein, these so-called type II proteins present challenges to understand the precise role they play. Additional structures of individual and multi-domain components of the NRPS enzymes will therefore provide a better understanding of the features that govern the domain interactions in these interesting enzyme systems. The high-resolution crystal structure of a free-standing carrier protein fromAcinetobacter baumanniithat belongs to a larger NRPS-containing operon, encoded by the ABBFA_003406–ABBFA_003399 genes ofA. baumanniistrain AB307-0294, that has been implicated inA. baumanniimotility, quorum sensing and biofilm formation, is presented here. Comparison with the closest structural homologs of other carrier proteins identifies the requirements for a conserved glycine residue and additional important sequence and structural requirements within the regions that interact with partner proteins.

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AGRIMI, G., M. A. Di NOIA, C. M. T. MAROBBIO, G. FIERMONTE, F. M. LASORSA, and F. PALMIERI. "Identification of the human mitochondrial S-adenosylmethionine transporter: bacterial expression, reconstitution, functional characterization and tissue distribution." Biochemical Journal 379, no. 1 (April 1, 2004): 183–90. http://dx.doi.org/10.1042/bj20031664.

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The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites and cofactors through this membrane, and connect cytoplasmic functions with others in the matrix. SAM (S-adenosylmethionine) has to be transported into the mitochondria where it is converted into S-adenosylhomocysteine in methylation reactions of DNA, RNA and proteins. The transport of SAM has been investigated in rat liver mitochondria, but no protein has ever been associated with this activity. By using information derived from the phylogenetically distant yeast mitochondrial carrier for SAM and from related human expressed sequence tags, a human cDNA sequence was completed. This sequence was overexpressed in bacteria, and its product was purified, reconstituted into phospholipid vesicles and identified from its transport properties as the human mitochondrial SAM carrier (SAMC). Unlike the yeast orthologue, SAMC catalysed virtually only countertransport, exhibited a higher transport affinity for SAM and was strongly inhibited by tannic acid and Bromocresol Purple. SAMC was found to be expressed in all human tissues examined and was localized to the mitochondria. The physiological role of SAMC is probably to exchange cytosolic SAM for mitochondrial S-adenosylhomocysteine. This is the first report describing the identification and characterization of the human SAMC and its gene.

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Colasante, Claudia, Vincent P. Alibu, Simon Kirchberger, Joachim Tjaden, Christine Clayton, and Frank Voncken. "Characterization and Developmentally Regulated Localization of the Mitochondrial Carrier Protein Homologue MCP6 from Trypanosoma brucei." Eukaryotic Cell 5, no. 8 (August 2006): 1194–205. http://dx.doi.org/10.1128/ec.00096-06.

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ABSTRACT Proteins of the mitochondrial carrier family (MCF) are located mainly in the inner mitochondrial membrane and mediate the transport of a large range of metabolic intermediates. The genome of Trypanosoma brucei harbors 29 genes encoding different MCF proteins. We describe here the characterization of MCP6, a novel T. brucei MCF protein. Sequence comparison and phylogenetic reconstruction revealed that MCP6 is closely related to different mitochondrial ADP/ATP and calcium-dependent solute carriers, including the ATP-Mg/Pi carrier of Homo sapiens. However, MCP6 lacks essential amino acids and sequence motifs conserved in these metabolite transporters, and functional reconstitution and transport assays with E. coli suggested that this protein indeed does not function as an ADP/ATP or ATP-Mg/Pi carrier. The subcellular localization of MCP6 is developmentally regulated: in bloodstream-form trypanosomes, the protein is predominantly glycosomal, whereas in the procyclic form, it is found mainly in the mitochondria. Depletion of MCP6 in procyclic trypanosomes resulted in growth inhibition, an increased cell size, aberrant numbers of nuclei and kinetoplasts, and abnormal kinetoplast morphology, suggesting that depletion of MCP6 inhibits division of the kinetoplast.

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Monroy-González, Zurisadai, Miguel A. Uc-Chuc, Ana O. Quintana-Escobar, Fátima Duarte-Aké, and Víctor M. Loyola-Vargas. "Characterization of the PIN Auxin Efflux Carrier Gene Family and Its Expression during Zygotic Embryogenesis in Persea americana." Plants 12, no. 12 (June 12, 2023): 2280. http://dx.doi.org/10.3390/plants12122280.

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Auxins are responsible for a large part of the plant development process. To exert their action, they must move throughout the plant and from cell to cell, which is why plants have developed complex transport systems for indole-3-acetic acid (IAA). These transporters involve proteins that transport IAA into cells, transporters that move IAA to or from different organelles, mainly the endoplasmic reticulum, and transporters that move IAA out of the cell. This research determined that Persea americana has 12 PIN transporters in its genome. The twelve transporters are expressed during different stages of development in P. americana zygotic embryos. Using different bioinformatics tools, we determined the type of transporter of each of the P. americana PIN proteins and their structure and possible location in the cell. We also predict the potential phosphorylation sites for each of the twelve-PIN proteins. The data show the presence of highly conserved sites for phosphorylation and those sites involved in the interaction with the IAA.

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Prohl, Corinna, Winfried Pelzer, Kerstin Diekert, Hanna Kmita, Tibor Bedekovics, Gyula Kispal, and Roland Lill. "The Yeast Mitochondrial Carrier Leu5p and Its Human Homologue Graves' Disease Protein Are Required for Accumulation of Coenzyme A in the Matrix." Molecular and Cellular Biology 21, no. 4 (February 15, 2001): 1089–97. http://dx.doi.org/10.1128/mcb.21.4.1089-1097.2001.

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ABSTRACT The transport of metabolites, coenzymes, and ions across the mitochondrial inner membrane is still poorly understood. In most cases, membrane transport is facilitated by the so-called mitochondrial carrier proteins. The yeast Saccharomyces cerevisiaecontains 35 members of the carrier family, but a function has been identified for only 13 proteins. Here, we investigated the yeast carrier Leu5p (encoded by the gene YHR002w) and its close human homologue Graves' disease protein. Leu5p is inserted into the mitochondrial inner membrane along the specialized import pathway used by carrier proteins. Deletion of LEU5 (strain Δleu5) was accompanied by a 15-fold reduction of mitochondrial coenzyme A (CoA) levels but did not affect the cytosolic CoA content. As a consequence, the activities of several mitochondrial CoA-dependent enzymes were strongly decreased in Δleu5 cells. Our in vitro and in vivo analyses assign a function to Leu5p in the accumulation of CoA in mitochondria, presumably by serving as a transporter of CoA or a precursor thereof. Expression of the Graves' disease protein in Δleu5 cells can replace the function of Leu5p, demonstrating that the human protein represents the orthologue of yeast Leu5p. The function of the human protein might not be directly linked to the disease, as antisera derived from patients with active Graves' disease do not recognize the protein after expression in yeast, suggesting that it does not represent a major autoantigen. The two carrier proteins characterized herein are the first components for which a role in the subcellular distribution of CoA has been identified.

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Voilquin, Laetitia, Massimo Lodi, Thomas Di Mattia, Marie-Pierre Chenard, Carole Mathelin, Fabien Alpy, and Catherine Tomasetto. "STARD3: A Swiss Army Knife for Intracellular Cholesterol Transport." Contact 2 (January 2019): 251525641985673. http://dx.doi.org/10.1177/2515256419856730.

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Intracellular cholesterol transport is a complex process involving specific carrier proteins. Cholesterol-binding proteins, such as the lipid transfer protein steroidogenic acute regulatory-related lipid transfer domain-3 (STARD3), are implicated in cholesterol movements between organelles. Indeed, STARD3 modulates intracellular cholesterol allocation by reducing it from the plasma membrane and favoring its passage from the endoplasmic reticulum (ER) to endosomes, where the protein is localized. STARD3 interacts with ER-anchored partners, notably vesicle-associated membrane protein-associated proteins (VAP-A and VAP-B) and motile sperm domain-containing 2 (MOSPD2), to create ER–endosome membrane contacts. Mechanistic studies showed that at ER–endosome contacts, STARD3 and VAP proteins build a molecular machine able to rapidly transfer cholesterol. This review presents the current knowledge on the molecular and cellular function of STARD3 in intracellular cholesterol traffic.

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Raizada, Pankaj, and Uma Sharma. "Extraction and Transport of Amino Acids Using Kryptofix 5 as Carrier through Liquid Membrane." Journal of Chemistry 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/701570.

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The present work explores membrane-mediated extraction and transport studies of amino acids through artificial bulk liquid membrane system with kryptofix 5 as a carrier. The various reaction parameters such as amino acid concentration, carrier concentration, time, pH, and stirring effect were studied to optimize reaction conditions. The stirring of source and receiving phases increased the efficiency of extraction process. Noncyclic receptor kryptofix 5 with five oxyethylene units and terminal aromatic donor end groups governs its transport and extraction efficiency. The extraction and transport efficiency followed the following trend: valine > alanine > glycine > threonine. Supported liquid membrane (SLM) studies were performed using cellulose nitrate, PTFE, eggshell, and onion membranes. The egg shell membrane support proved to be most efficient due to intricate network of water insoluble proteins fibers with very high surface area and homogeneity.

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Upadhyay, Ravi Kant. "Transendothelial Transport and Its Role in Therapeutics." International Scholarly Research Notices 2014 (August 27, 2014): 1–39. http://dx.doi.org/10.1155/2014/309404.

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Present review paper highlights role of BBB in endothelial transport of various substances into the brain. More specifically, permeability functions of BBB in transendothelial transport of various substances such as metabolic fuels, ethanol, amino acids, proteins, peptides, lipids, vitamins, neurotransmitters, monocarbxylic acids, gases, water, and minerals in the peripheral circulation and into the brain have been widely explained. In addition, roles of various receptors, ATP powered pumps, channels, and transporters in transport of vital molecules in maintenance of homeostasis and normal body functions have been described in detail. Major role of integral membrane proteins, carriers, or transporters in drug transport is highlighted. Both diffusion and carrier mediated transport mechanisms which facilitate molecular trafficking through transcellular route to maintain influx and outflux of important nutrients and metabolic substances are elucidated. Present review paper aims to emphasize role of important transport systems with their recent advancements in CNS protection mainly for providing a rapid clinical aid to patients. This review also suggests requirement of new well-designed therapeutic strategies mainly potential techniques, appropriate drug formulations, and new transport systems for quick, easy, and safe delivery of drugs across blood brain barrier to save the life of tumor and virus infected patients.

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Grevel, Alexander, and Thomas Becker. "Porins as helpers in mitochondrial protein translocation." Biological Chemistry 401, no. 6-7 (May 26, 2020): 699–708. http://dx.doi.org/10.1515/hsz-2019-0438.

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AbstractMitochondria import the vast majority of their proteins via dedicated protein machineries. The translocase of the outer membrane (TOM complex) forms the main entry site for precursor proteins that are produced on cytosolic ribosomes. Subsequently, different protein sorting machineries transfer the incoming preproteins to the mitochondrial outer and inner membranes, the intermembrane space, and the matrix. In this review, we highlight the recently discovered role of porin, also termed voltage-dependent anion channel (VDAC), in mitochondrial protein biogenesis. Porin forms the major channel for metabolites and ions in the outer membrane of mitochondria. Two different functions of porin in protein translocation have been reported. First, it controls the formation of the TOM complex by modulating the integration of the central receptor Tom22 into the mature translocase. Second, porin promotes the transport of carrier proteins toward the carrier translocase (TIM22 complex), which inserts these preproteins into the inner membrane. Therefore, porin acts as a coupling factor to spatially coordinate outer and inner membrane transport steps. Thus, porin links metabolite transport to protein import, which are both essential for mitochondrial function and biogenesis.

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Nunes-Nesi, Adriano, João Henrique F. Cavalcanti, and Alisdair R. Fernie. "Characterization of In Vivo Function(s) of Members of the Plant Mitochondrial Carrier Family." Biomolecules 10, no. 9 (August 24, 2020): 1226. http://dx.doi.org/10.3390/biom10091226.

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Although structurally related, mitochondrial carrier family (MCF) proteins catalyze the specific transport of a range of diverse substrates including nucleotides, amino acids, dicarboxylates, tricarboxylates, cofactors, vitamins, phosphate and H+. Despite their name, they do not, however, always localize to the mitochondria, with plasma membrane, peroxisomal, chloroplast and thylakoid and endoplasmic reticulum localizations also being reported. The existence of plastid-specific MCF proteins is suggestive that the evolution of these proteins occurred after the separation of the green lineage. That said, plant-specific MCF proteins are not all plastid-localized, with members also situated at the endoplasmic reticulum and plasma membrane. While by no means yet comprehensive, the in vivo function of a wide range of these transporters is carried out here, and we discuss the employment of genetic variants of the MCF as a means to provide insight into their in vivo function complementary to that obtained from studies following their reconstitution into liposomes.

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Palmieri, Luigi, Nathalie Picault, Roberto Arrigoni, Evelyne Besin, Ferdinando Palmieri, and Michael Hodges. "Molecular identification of three Arabidopsis thaliana mitochondrial dicarboxylate carrier isoforms: organ distribution, bacterial expression, reconstitution into liposomes and functional characterization." Biochemical Journal 410, no. 3 (February 27, 2008): 621–29. http://dx.doi.org/10.1042/bj20070867.

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Screening of the Arabidopsis thaliana genome revealed three potential homologues of mammalian and yeast mitochondrial DICs (dicarboxylate carriers) designated as DIC1, DIC2 and DIC3, each belonging to the mitochondrial carrier protein family. DIC1 and DIC2 are broadly expressed at comparable levels in all the tissues investigated. DIC1–DIC3 have been reported previously as uncoupling proteins, but direct transport assays with recombinant and reconstituted DIC proteins clearly demonstrate that their substrate specificity is unique to plants, showing the combined characteristics of the DIC and oxaloacetate carrier in yeast. Indeed, the Arabidopsis DICs transported a wide range of dicarboxylic acids including malate, oxaloacetate and succinate as well as phosphate, sulfate and thiosulfate at high rates, whereas 2-oxoglutarate was revealed to be a very poor substrate. The role of these plant mitochondrial DICs is discussed with respect to other known mitochondrial carrier family members including uncoupling proteins. It is proposed that plant DICs constitute the membrane component of several metabolic processes including the malate–oxaloacetate shuttle, the most important redox connection between the mitochondria and the cytosol.

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TIRIBELLI, CLAUDIO, STEFANO BELLENTANI, GIAN CARLO LUNAZZI, and GIAN LUIGI SOTTOCASA. "Role and nature of plasma membrane carrier proteins in the hepatic transport of organic anions." Journal of Gastroenterology and Hepatology 4, no. 2 (April 1989): 195–205. http://dx.doi.org/10.1111/j.1440-1746.1989.tb00825.x.

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Froschauer, Elisabeth M., Rudolf J. Schweyen, and Gerlinde Wiesenberger. "The yeast mitochondrial carrier proteins Mrs3p/Mrs4p mediate iron transport across the inner mitochondrial membrane." Biochimica et Biophysica Acta (BBA) - Biomembranes 1788, no. 5 (May 2009): 1044–50. http://dx.doi.org/10.1016/j.bbamem.2009.03.004.

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Journal articles on the topic 'Carrier and Transport Proteins'

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