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Zeitschriftenartikel zum Thema „Gating mechanism“

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Veröffentlicht am 25. Mai 2024

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Ulbricht, Mathias. "Gating mechanism under pressure." Nature 519, no. 7541 (2015): 41–42. http://dx.doi.org/10.1038/519041a.

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Csanády, László. "Application of rate-equilibrium free energy relationship analysis to nonequilibrium ion channel gating mechanisms." Journal of General Physiology 134, no. 2 (2009): 129–36. http://dx.doi.org/10.1085/jgp.200910268.

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Rate-equilibrium free energy relationship (REFER) analysis provides information on transition-state structures and has been applied to reveal the temporal sequence in which the different regions of an ion channel protein move during a closed–open conformational transition. To date, the theory used to interpret REFER relationships has been developed only for equilibrium mechanisms. Gating of most ion channels is an equilibrium process, but recently several ion channels have been identified to have retained nonequilibrium traits in their gating cycles, inherited from transporter-like ancestors. So far it has not been examined to what extent REFER analysis is applicable to such systems. By deriving the REFER relationships for a simple nonequilibrium mechanism, this paper addresses whether an equilibrium mechanism can be distinguished from a nonequilibrium one by the characteristics of their REFER plots, and whether information on the transition-state structures can be obtained from REFER plots for gating mechanisms that are known to be nonequilibrium cycles. The results show that REFER plots do not carry information on the equilibrium nature of the underlying gating mechanism. Both equilibrium and nonequilibrium mechanisms can result in linear or nonlinear REFER plots, and complementarity of REFER slopes for opening and closing transitions is a trivial feature true for any mechanism. Additionally, REFER analysis provides limited information about the transition-state structures for gating schemes that are known to be nonequilibrium cycles.

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Enkvetchakul, D., and C. G. Nichols. "Gating Mechanism of KATP Channels." Journal of General Physiology 122, no. 5 (2003): 471–80. http://dx.doi.org/10.1085/jgp.200308878.

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Fu, Tianmin. "Molecular Mechanism of TRPM2 Gating." Biophysical Journal 116, no. 3 (2019): 299a—300a. http://dx.doi.org/10.1016/j.bpj.2018.11.1624.

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Zhao, Piao, Cheng Tang, Yuqin Yang, et al. "A new polymodal gating model of the proton-activated chloride channel." PLOS Biology 21, no. 9 (2023): e3002309. http://dx.doi.org/10.1371/journal.pbio.3002309.

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The proton–activated chloride (PAC) channel plays critical roles in ischemic neuron death, but its activation mechanisms remain elusive. Here, we investigated the gating of PAC channels using its novel bifunctional modulator C77304. C77304 acted as a weak activator of the PAC channel, causing moderate activation by acting on its proton gating. However, at higher concentrations, C77304 acted as a weak inhibitor, suppressing channel activity. This dual function was achieved by interacting with 2 modulatory sites of the channel, each with different affinities and dependencies on the channel’s state. Moreover, we discovered a protonation–independent voltage activation of the PAC channel that appears to operate through an ion–flux gating mechanism. Through scanning–mutagenesis and molecular dynamics simulation, we confirmed that E181, E257, and E261 in the human PAC channel serve as primary proton sensors, as their alanine mutations eliminated the channel’s proton gating while sparing the voltage–dependent gating. This proton–sensing mechanism was conserved among orthologous PAC channels from different species. Collectively, our data unveils the polymodal gating and proton–sensing mechanisms in the PAC channel that may inspire potential drug development.

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Elinder, Fredrik, and Peter Århem. "Metal ion effects on ion channel gating." Quarterly Reviews of Biophysics 36, no. 4 (2003): 373–427. http://dx.doi.org/10.1017/s0033583504003932.

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1. Introduction 3742. Metals in biology 3783. The targets: structure and function of ion channels 3804. General effects of metal ions on channels 3824.1 Three types of general effect 3824.2 The main regulators 3835. Effects on gating: mechanisms and models 3845.1 Screening surface charges (Mechanism A) 3875.1.1 The classical approach 3875.1.1.1 Applying the Grahame equation 3885.1.2 A one-site approach 3915.2 Binding and electrostatically modifying the voltage sensor (Mechanism B) 3915.2.1 The classical model 3915.2.1.1 The classical model as state diagram – introducing basic channel kinetics 3925.2.2 A one-site approach 3955.2.2.1 Explaining state-dependent binding – a simple electrostatic mechanism 3955.2.2.2 The relation between models assuming binding to smeared and to discrete charges 3965.2.2.3 The special case of Zn2+ – no binding in the open state 3965.2.2.4 Opposing effects of Cd2+ on hyperpolarization-activated channels 3985.3 Binding and interacting non-electrostatically with the voltage sensor (Mechanism C) 3985.3.1 Combining mechanical slowing of opening and closing with electrostatic modification of voltage sensor 4005.4 Binding to the pore – a special case of one-site binding models (Mechanism D) 4005.4.1 Voltage-dependent pore-block – adding extra gating 4015.4.2 Coupling pore block to gating 4025.4.2.1 The basic model again 4025.4.2.2 A special case – Ca2+ as necessary cofactor for closing 4035.4.2.3 Expanding the basic model – Ca2+ affecting a voltage-independent step 4045.5 Summing up 4056. Quantifying the action: comparing the metal ions 4076.1 Steady-state parameters are equally shifted 4076.2 Different metal ions cause different shifts 4086.3 Different metal ions slow gating differently 4106.4 Block of ion channels 4127. Locating the sites of action 4127.1 Fixed surface charges involved in screening 4137.2 Binding sites 4137.2.1 Group 2 ions 4147.2.2 Group 12 ions 4148. Conclusions and perspectives 4159. Appendix 41610. Acknowledgements 41811. References 418Metal ions affect ion channels either by blocking the current or by modifying the gating. In the present review we analyse the effects on the gating of voltage-gated channels. We show that the effects can be understood in terms of three main mechanisms. Mechanism A assumes screening of fixed surface charges. Mechanism B assumes binding to fixed charges and an associated electrostatic modification of the voltage sensor. Mechanism C assumes binding and an associated non-electrostatic modification of the gating. To quantify the non-electrostatic effect we introduced a slowing factor, A. A fourth mechanism (D) is binding to the pore with a consequent pore block, and could be a special case of Mechanisms B or C. A further classification considers whether the metal ion affects a single site or multiple sites. Analysing the properties of these mechanisms and the vast number of studies of metal ion effects on different voltage-gated ion channels we conclude that group 2 ions mainly affect channels by classical screening (a version of Mechanism A). The transition metals and the Zn group ions mainly bind to the channel and electrostatically modify the gating (Mechanism B), causing larger shifts of the steady-state parameters than the group 2 ions, but also different shifts of activation and deactivation curves. The lanthanides mainly bind to the channel and both electrostatically and non-electrostatically modify the gating (Mechanisms B and C). With the exception of the ether-à-go-go-like channels, most channel types show remarkably similar ion-specific sensitivities.

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Navarro, Marco A., Lorin S. Milescu, and Mirela Milescu. "Unlocking the gating mechanism of Kv2.1 using guangxitoxin." Journal of General Physiology 151, no. 3 (2018): 275–78. http://dx.doi.org/10.1085/jgp.201812254.

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Lopez, William, Jayalakshmi Ramachandran, Abdelaziz Alsamarah, Yun Luo, Andrew L. Harris, and Jorge E. Contreras. "Mechanism of gating by calcium in connexin hemichannels." Proceedings of the National Academy of Sciences 113, no. 49 (2016): E7986—E7995. http://dx.doi.org/10.1073/pnas.1609378113.

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Aberrant opening of nonjunctional connexin hemichannels at the plasma membrane is associated with many diseases, including ischemia and muscular dystrophy. Proper control of hemichannel opening is essential to maintain cell viability and is achieved by physiological levels of extracellular Ca2+, which drastically reduce hemichannel activity. Here we examined the role of conserved charged residues that form electrostatic networks near the extracellular entrance of the connexin pore, a region thought to be involved in gating rearrangements of hemichannels. Molecular dynamics simulations indicate discrete sites for Ca2+ interaction and consequent disruption of salt bridges in the open hemichannels. Experimentally, we found that disruption of these salt bridges by mutations facilitates hemichannel closing. Two negatively charged residues in these networks are putative Ca2+ binding sites, forming a Ca2+-gating ring near the extracellular entrance of the pore. Accessibility studies showed that this Ca2+-bound gating ring does not prevent access of ions or small molecules to positions deeper into the pore, indicating that the physical gate is below the Ca2+-gating ring. We conclude that intra- and intersubunit electrostatic networks at the extracellular entrance of the hemichannel pore play critical roles in hemichannel gating reactions and are tightly controlled by extracellular Ca2+. Our findings provide a general mechanism for Ca2+ gating among different connexin hemichannel isoforms.

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Bompadre, Silvia G., Tomohiko Ai, Jeong Han Cho, et al. "CFTR Gating I." Journal of General Physiology 125, no. 4 (2005): 361–75. http://dx.doi.org/10.1085/jgp.200409227.

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The CFTR chloride channel is activated by phosphorylation of serine residues in the regulatory (R) domain and then gated by ATP binding and hydrolysis at the nucleotide binding domains (NBDs). Studies of the ATP-dependent gating process in excised inside-out patches are very often hampered by channel rundown partly caused by membrane-associated phosphatases. Since the severed ΔR-CFTR, whose R domain is completely removed, can bypass the phosphorylation-dependent regulation, this mutant channel might be a useful tool to explore the gating mechanisms of CFTR. To this end, we investigated the regulation and gating of the ΔR-CFTR expressed in Chinese hamster ovary cells. In the cell-attached mode, basal ΔR-CFTR currents were always obtained in the absence of cAMP agonists. Application of cAMP agonists or PMA, a PKC activator, failed to affect the activity, indicating that the activity of ΔR-CFTR channels is indeed phosphorylation independent. Consistent with this conclusion, in excised inside-out patches, application of the catalytic subunit of PKA did not affect ATP-induced currents. Similarities of ATP-dependent gating between wild type and ΔR-CFTR make this phosphorylation-independent mutant a useful system to explore more extensively the gating mechanisms of CFTR. Using the ΔR-CFTR construct, we studied the inhibitory effect of ADP on CFTR gating. The Ki for ADP increases as the [ATP] is increased, suggesting a competitive mechanism of inhibition. Single channel kinetic analysis reveals a new closed state in the presence of ADP, consistent with a kinetic mechanism by which ADP binds at the same site as ATP for channel opening. Moreover, we found that the open time of the channel is shortened by as much as 54% in the presence of ADP. This unexpected result suggests another ADP binding site that modulates channel closing.

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Tiffner, Adéla, Lena Maltan, Sarah Weiß, and Isabella Derler. "The Orai Pore Opening Mechanism." International Journal of Molecular Sciences 22, no. 2 (2021): 533. http://dx.doi.org/10.3390/ijms22020533.

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Cell survival and normal cell function require a highly coordinated and precise regulation of basal cytosolic Ca2+ concentrations. The primary source of Ca2+ entry into the cell is mediated by the Ca2+ release-activated Ca2+ (CRAC) channel. Its action is stimulated in response to internal Ca2+ store depletion. The fundamental constituents of CRAC channels are the Ca2+ sensor, stromal interaction molecule 1 (STIM1) anchored in the endoplasmic reticulum, and a highly Ca2+-selective pore-forming subunit Orai1 in the plasma membrane. The precise nature of the Orai1 pore opening is currently a topic of intensive research. This review describes how Orai1 gating checkpoints in the middle and cytosolic extended transmembrane regions act together in a concerted manner to ensure an opening-permissive Orai1 channel conformation. In this context, we highlight the effects of the currently known multitude of Orai1 mutations, which led to the identification of a series of gating checkpoints and the determination of their role in diverse steps of the Orai1 activation cascade. The synergistic action of these gating checkpoints maintains an intact pore geometry, settles STIM1 coupling, and governs pore opening. We describe the current knowledge on Orai1 channel gating mechanisms and summarize still open questions of the STIM1–Orai1 machinery.

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García, Isaac E., Felipe Villanelo, Gustavo F. Contreras, et al. "The syndromic deafness mutation G12R impairs fast and slow gating in Cx26 hemichannels." Journal of General Physiology 150, no. 5 (2018): 697–711. http://dx.doi.org/10.1085/jgp.201711782.

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Mutations in connexin 26 (Cx26) hemichannels can lead to syndromic deafness that affects the cochlea and skin. These mutations lead to gain-of-function hemichannel phenotypes by unknown molecular mechanisms. In this study, we investigate the biophysical properties of the syndromic mutant Cx26G12R (G12R). Unlike wild-type Cx26, G12R macroscopic hemichannel currents do not saturate upon depolarization, and deactivation is faster during hyperpolarization, suggesting that these channels have impaired fast and slow gating. Single G12R hemichannels show a large increase in open probability, and transitions to the subconductance state are rare and short-lived, demonstrating an inoperative fast gating mechanism. Molecular dynamics simulations indicate that G12R causes a displacement of the N terminus toward the cytoplasm, favoring an interaction between R12 in the N terminus and R99 in the intracellular loop. Disruption of this interaction recovers the fast and slow voltage-dependent gating mechanisms. These results suggest that the mechanisms of fast and slow gating in connexin hemichannels are coupled and provide a molecular mechanism for the gain-of-function phenotype displayed by the syndromic G12R mutation.

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Osteen, J. D., R. Barro-Soria, S. Robey, K. J. Sampson, R. S. Kass, and H. P. Larsson. "Allosteric gating mechanism underlies the flexible gating of KCNQ1 potassium channels." Proceedings of the National Academy of Sciences 109, no. 18 (2012): 7103–8. http://dx.doi.org/10.1073/pnas.1201582109.

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Törnroth-Horsefield, Susanna, Yi Wang, Kristina Hedfalk, et al. "Structural mechanism of plant aquaporin gating." Nature 439, no. 7077 (2005): 688–94. http://dx.doi.org/10.1038/nature04316.

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Magleby, Karl L. "Gating Mechanism of BK (Slo1) Channels." Journal of General Physiology 121, no. 2 (2003): 81–96. http://dx.doi.org/10.1085/jgp.20028721.

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Clemens, Daniel M., Juan A. Freites, Karinne L. Németh-Cahalan, Douglas J. Tobias, and James E. Hall. "CaM Induced Gating Mechanism of AQP0." Biophysical Journal 102, no. 3 (2012): 397a. http://dx.doi.org/10.1016/j.bpj.2011.11.2169.

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Beckstein, Oliver, Philip C. Biggin, and Mark S. P. Sansom. "A Hydrophobic Gating Mechanism for Nanopores." Journal of Physical Chemistry B 105, no. 51 (2001): 12902–5. http://dx.doi.org/10.1021/jp012233y.

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Fahlke, Christoph, Christine Dürr, and Alfred L. George. "Mechanism of Ion Permeation in Skeletal Muscle Chloride Channels." Journal of General Physiology 110, no. 5 (1997): 551–64. http://dx.doi.org/10.1085/jgp.110.5.551.

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Voltage-gated Cl− channels belonging to the ClC family exhibit unique properties of ion permeation and gating. We functionally probed the conduction pathway of a recombinant human skeletal muscle Cl− channel (hClC-1) expressed both in Xenopus oocytes and in a mammalian cell line by investigating block by extracellular or intracellular I− and related anions. Extracellular and intracellular I− exert blocking actions on hClC-1 currents that are both concentration and voltage dependent. Similar actions were observed for a variety of other halide (Br−) and polyatomic (SCN−, NO3−, CH3SO3−) anions. In addition, I− block is accompanied by gating alterations that differ depending on which side of the membrane the blocker is applied. External I− causes a shift in the voltage-dependent probability that channels exist in three definable kinetic states (fast deactivating, slow deactivating, nondeactivating), while internal I− slows deactivation. These different effects on gating properties can be used to distinguish two functional ion binding sites within the hClC-1 pore. We determined KD values for I− block in three distinct kinetic states and found that binding of I− to hClC-1 is modulated by the gating state of the channel. Furthermore, estimates of electrical distance for I− binding suggest that conformational changes affecting the two ion binding sites occur during gating transitions. These results have implications for understanding mechanisms of ion selectivity in hClC-1, and for defining the intimate relationship between gating and permeation in ClC channels.

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Liu, Li Jun, and Ying Lei. "Mechanism of Bio-Inspired Ultrasensitive Low Frequency Sensor with Mechanics Analysis." Applied Mechanics and Materials 252 (December 2012): 162–66. http://dx.doi.org/10.4028/www.scientific.net/amm.252.162.

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It is essential to develop ultrasensitive low frequency sensors for efficient structural health monitoring and early warning of natural disasters. Many fishes have been reported to have acute sensitivity to low frequency. Based on the mechanism of the infrasound sensitivity of fish, mechanism of bio-inspired ultrasensitive low frequency sensor is explored by a mechanical model with gating spring hypothesis for simulating the mechanical-electricity transduction of the hair cell in fish ear. Numerical analyses of the mechanical model subject to static and dynamic loading are conducted respectively by OpenSees. Under static loading, displacement response of gating model is more sensitive to weak loading due to the opening of gating spring. Under dynamic loading, the gating model is more acute sensitive to low frequency and weak loading due to the adaptive amplification of gating spring. This mechanical function can be used as the theoretical basis for the design of ultrasensitive bio-inspired low frequency sensors.

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Nordin, Nurhuda, Albert Guskov, Terri Phua, et al. "Exploring the structure and function of Thermotoga maritima CorA reveals the mechanism of gating and ion selectivity in Co2+/Mg2+ transport." Biochemical Journal 451, no. 3 (2013): 365–74. http://dx.doi.org/10.1042/bj20121745.

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The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as primary substrates. The molecular mechanism of its function, including ion selectivity and gating, has not been fully characterized. Recently we reported a new structure of a CorA homologue from Methanocaldococcus jannaschii, which provided novel structural details that offered the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a closed hydrophobic one. In the present study we report functional evidence for this novel gating mechanism in the Thermotoga maritima CorA together with an improved crystal structure of this CorA to 2.7 Å (1 Å=0.1 nm) resolution. The latter reveals the organization of the selectivity filter to be similar to that of M. jannaschii CorA and also the previously unknown organization of the second signature motif of the CorA family. The proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the regulatory binding sites. Additionally, our data suggest that the preference of this CorA for Co2+ over Mg2+ is controlled by the presence of threonine side chains in the channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA family as they are regulated by the highly conserved amino acids.

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Kim, Kyu Min, Tharaka Wijerathne, Jin-Hoe Hur, et al. "Distinct gating mechanism of SOC channel involving STIM–Orai coupling and an intramolecular interaction of Orai in Caenorhabditis elegans." Proceedings of the National Academy of Sciences 115, no. 20 (2018): E4623—E4632. http://dx.doi.org/10.1073/pnas.1714986115.

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Store-operated calcium entry (SOCE), an important mechanism of Ca2+ signaling in a wide range of cell types, is mediated by stromal interaction molecule (STIM), which senses the depletion of endoplasmic reticulum Ca2+ stores and binds and activates Orai channels in the plasma membrane. This inside-out mechanism of Ca2+ signaling raises an interesting question about the evolution of SOCE: How did these two proteins existing in different cellular compartments evolve to interact with each other? We investigated the gating mechanism of Caenorhabditis elegans Orai channels. Our analysis revealed a mechanism of Orai gating by STIM binding to the intracellular 2–3 loop of Orai in C. elegans that is radically different from Orai gating by STIM binding to the N and C termini of Orai in mammals. In addition, we found that the conserved hydrophobic amino acids in the 2–3 loop of Orai1 are important for the oligomerization and gating of channels and are regulated via an intramolecular interaction mechanism mediated by the N and C termini of Orai1. This study identifies a previously unknown SOCE mechanism in C. elegans and suggests that, while the STIM–Orai interaction is conserved between invertebrates and mammals, the gating mechanism for Orai channels differs considerably.

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Engh, Anita M., José D. Faraldo-Gómez, and Merritt Maduke. "The Mechanism of Fast-Gate Opening in ClC-0." Journal of General Physiology 130, no. 4 (2007): 335–49. http://dx.doi.org/10.1085/jgp.200709759.

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ClC-0 is a chloride channel whose gating is sensitive to both voltage and chloride. Based on analysis of gating kinetics using single-channel recordings, a five-state model was proposed to describe the dependence of ClC-0 fast-gate opening on voltage and external chloride (Chen, T.-Y., and C. Miller. 1996. J. Gen. Physiol. 108:237–250). We aimed to use this five-state model as a starting point for understanding the structural changes that occur during gating. Using macroscopic patch recordings, we were able to reproduce the effects of voltage and chloride that were reported by Chen and Miller and to fit our opening rate constant data to the five-state model. Upon further analysis of both our data and those of Chen and Miller, we learned that in contrast to their conclusions, (a) the features in the data are not adequate to rule out a simpler four-state model, and (b) the chloride-binding step is voltage dependent. In order to be able to evaluate the effects of mutants on gating (described in the companion paper, see Engh et al. on p. 351 of this issue), we developed a method for determining the error on gating model parameters, and evaluated the sources of this error. To begin to mesh the kinetic model(s) with the known CLC structures, a model of ClC-0 was generated computationally based on the X-ray crystal structure of the prokaryotic homolog ClC-ec1. Analysis of pore electrostatics in this homology model suggests that at least two of the conclusions derived from the gating kinetics analysis are consistent with the known CLC structures: (1) chloride binding is necessary for channel opening, and (2) chloride binding to any of the three known chloride-binding sites must be voltage dependent.

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Borschel, William F., Jason M. Myers, Eileen M. Kasperek, et al. "Gating reaction mechanism of neuronal NMDA receptors." Journal of Neurophysiology 108, no. 11 (2012): 3105–15. http://dx.doi.org/10.1152/jn.00551.2012.

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The activation mechanisms of recombinant N-methyl-d-aspartate receptors (NRs) have been established in sufficient detail to account for their single channel and macroscopic responses; however, the reaction mechanism of native NRs remains uncertain due to indetermination of the isoforms expressed and possible neuron-specific factors. To delineate the activation mechanism of native NRs, we examined the kinetic properties of currents generated by individual channels located at the soma of cultured rat neurons. Cells were dissociated from the embryonic cerebral cortex or hippocampus, and on-cell single channel recordings were done between 4 and 50 days in vitro (DIV). We observed two types of kinetics that correlated with the age of the culture. When we segregated recordings by culture age, we found that receptors recorded from early (4–33 DIV) and late (25–50 DIV) cultures had smaller unitary conductances but had kinetic profiles that matched closely those of recombinant 2B- or 2A-containing receptors, respectively. In addition, we examined the effects of cotransfection with postsynaptic density protein 95 or neuropilin tolloid-like protein 1 on recombinant receptors expressed in human embryonic kidney-293 cells. Our results add support to the view that neuronal cultures recapitulate the developmental patterns of receptor expression observed in the intact animal and demonstrate that the activation mechanism of somatic neuronal NRs is similar to that described for recombinant receptors of defined subunit composition.

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Shim, Jeong-Yon. "Expert-Knowledge Gating Mechanism in the Hierarchical Modular System." Journal of Advanced Computational Intelligence and Intelligent Informatics 8, no. 4 (2004): 410–14. http://dx.doi.org/10.20965/jaciii.2004.p0410.

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To maximize the efficiency of knowledge learning, it is essential that the knowledge system itself be well structured. Well designed knowledge systems make easy to access for knowledge acquisition and extraction. Expert knowledge plays a role controlling. We propose a Hierarchical modular system with an expert-knowledge gating mechanism that consists of mechanisms for acquiring knowledge, constructing associative memory and enabling knowledge inference and extraction based on expert-knowledge gating. We applied this to medical diagnostics for classifying Viruses (coxackie, echovirus and cold virus), Rhinitis (Nonallergic and allergic) and tested using symptom data.

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Wang, Longfei, Tian-Min Fu, Yiming Zhou, Shiyu Xia, Anna Greka, and Hao Wu. "Structures and gating mechanism of human TRPM2." Science 362, no. 6421 (2018): eaav4809. http://dx.doi.org/10.1126/science.aav4809.

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Transient receptor potential (TRP) melastatin 2 (TRPM2) is a cation channel associated with numerous diseases. It has a C-terminal NUDT9 homology (NUDT9H) domain responsible for binding adenosine diphosphate (ADP)–ribose (ADPR), and both ADPR and calcium (Ca2+) are required for TRPM2 activation. Here we report cryo–electron microscopy structures of human TRPM2 alone, with ADPR, and with ADPR and Ca2+. NUDT9H forms both intra- and intersubunit interactions with the N-terminal TRPM homology region (MHR1/2/3) in the apo state but undergoes conformational changes upon ADPR binding, resulting in rotation of MHR1/2 and disruption of the intersubunit interaction. The binding of Ca2+ further engages transmembrane helices and the conserved TRP helix to cause conformational changes at the MHR arm and the lower gating pore to potentiate channel opening. These findings explain the molecular mechanism of concerted TRPM2 gating by ADPR and Ca2+ and provide insights into the gating mechanism of other TRP channels.

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Jones, Lisa P., Shao-kui Wei та David T. Yue. "Mechanism of Auxiliary Subunit Modulation of Neuronal α1E Calcium Channels". Journal of General Physiology 112, № 2 (1998): 125–43. http://dx.doi.org/10.1085/jgp.112.2.125.

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Voltage-gated calcium channels are composed of a main pore-forming α1 moiety, and one or more auxiliary subunits (β, α2δ) that modulate channel properties. Because modulatory properties may vary greatly with different channels, expression systems, and protocols, it is advantageous to study subunit regulation with a uniform experimental strategy. Here, in HEK 293 cells, we examine the expression and activation gating of α1E calcium channels in combination with a β (β1–β4) and/or the α2δ subunit, exploiting both ionic- and gating-current measurements. Furthermore, to explore whether more than one auxiliary subunit can concomitantly specify gating properties, we investigate the effects of cotransfecting α2δ with β subunits, of transfecting two different β subunits simultaneously, and of COOH-terminal truncation of α1E to remove a second β binding site. The main results are as follows. (a) The α2δ and β subunits modulate α1E in fundamentally different ways. The sole effect of α2δ is to increase current density by elevating channel density. By contrast, though β subunits also increase functional channel number, they also enhance maximum open probability (Gmax/Qmax) and hyperpolarize the voltage dependence of ionic-current activation and gating-charge movement, all without discernible effect on activation kinetics. Different β isoforms produce nearly indistinguishable effects on activation. However, β subunits produced clear, isoform-specific effects on inactivation properties. (b) All the β subunit effects can be explained by a gating model in which subunits act only on weakly voltage-dependent steps near the open state. (c) We find no clear evidence for simultaneous modulation by two different β subunits. (d) The modulatory features found here for α1E do not generalize uniformly to other α1 channel types, as α1C activation gating shows marked β isoform dependence that is absent for α1E. Together, these results help to establish a more comprehensive picture of auxiliary-subunit regulation of α1E calcium channels.

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Giangiacomo, Kathleen M., Augustus Kamassah, Guy Harris, and Owen B. McManus. "Mechanism of Maxi-K Channel Activation by Dehydrosoyasaponin-I." Journal of General Physiology 112, no. 4 (1998): 485–501. http://dx.doi.org/10.1085/jgp.112.4.485.

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Dehydrosoyasaponin-I (DHS-I) is a potent activator of high-conductance, calcium-activated potassium (maxi-K) channels. Interaction of DHS-I with maxi-K channels from bovine aortic smooth muscle was studied after incorporating single channels into planar lipid bilayers. Nanomolar amounts of intracellular DHS-I caused the appearance of discrete episodes of high channel open probability interrupted by periods of apparently normal activity. Statistical analysis of these periods revealed two clearly separable gating modes that likely reflect binding and unbinding of DHS-I. Kinetic analysis of durations of DHS-I-modified modes suggested DHS-I activates maxi-K channels through a high-order reaction. Average durations of DHS-I-modified modes increased with DHS-I concentration, and distributions of these mode durations contained two or more exponential components. In addition, dose-dependent increases in channel open probability from low initial values were high order with average Hill slopes of 2.4–2.9 under different conditions, suggesting at least three to four DHS-I molecules bind to maximally activate the channel. Changes in membrane potential over a 60-mV range appeared to have little effect on DHS-I binding. DHS-I modified calcium- and voltage-dependent channel gating. 100 nM DHS-I caused a threefold decrease in concentration of calcium required to half maximally open channels. DHS-I shifted the midpoint voltage for channel opening to more hyperpolarized potentials with a maximum shift of −105 mV. 100 nM DHS-I had a larger effect on voltage-dependent compared with calcium-dependent channel gating, suggesting DHS-I may differentiate these gating mechanisms. A model specifying four identical, noninteracting binding sites, where DHS-I binds to open conformations with 10–20-fold higher affinity than to closed conformations, explained changes in voltage-dependent gating and DHS-I-induced modes. This model of channel activation by DHS-I may provide a framework for understanding protein structures underlying maxi-K channel gating, and may provide a basis for understanding ligand activation of other ion channels.

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Liu, Huawen, Xueting Zhao, Ning Jia, et al. "Engineering of thermo-/pH-responsive membranes with enhanced gating coefficients, reversible behaviors and self-cleaning performance through acetic acid boosted microgel assembly." Journal of Materials Chemistry A 6, no. 25 (2018): 11874–83. http://dx.doi.org/10.1039/c8ta04010a.

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Nureki, O. "Gating Control; Mechanism of Magnesium Transporter MgtE." Journal of Proteomics & Bioinformatics S2, no. 01 (2008): 021. http://dx.doi.org/10.4172/jpb.s1000025.

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Jensen, M. O., V. Jogini, D. W. Borhani, A. E. Leffler, R. O. Dror, and D. E. Shaw. "Mechanism of Voltage Gating in Potassium Channels." Science 336, no. 6078 (2012): 229–33. http://dx.doi.org/10.1126/science.1216533.

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Shin, Yeon-Kyun. "K+ channel gating mechanism proposed using EPR." Nature Structural Biology 5, no. 6 (1998): 418–20. http://dx.doi.org/10.1038/nsb0698-418.

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Sukharev, Sergei, Stewart R. Durell, and H. Robert Guy. "Structural Models of the MscL Gating Mechanism." Biophysical Journal 81, no. 2 (2001): 917–36. http://dx.doi.org/10.1016/s0006-3495(01)75751-7.

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Sineshchekov, Oleg A., Elena G. Govorunova, Hai Li, and John L. Spudich. "Gating mechanisms of a natural anion channelrhodopsin." Proceedings of the National Academy of Sciences 112, no. 46 (2015): 14236–41. http://dx.doi.org/10.1073/pnas.1513602112.

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Anion channelrhodopsins (ACRs) are a class of light-gated channels recently identified in cryptophyte algae that provide unprecedented fast and powerful hyperpolarizing tools for optogenetics. Analysis of photocurrents generated byGuillardia thetaACR 1 (GtACR1) and its mutants in response to laser flashes showed thatGtACR1 gating comprises two separate mechanisms with opposite dependencies on the membrane voltage and pH and involving different amino acid residues. The first mechanism, characterized by slow opening and fast closing of the channel, is regulated by Glu-68. Neutralization of this residue (the E68Q mutation) specifically suppressed this first mechanism, but did not eliminate it completely at high pH. Our data indicate the involvement of another, yet-unidentified pH-sensitive group X. Introducing a positive charge at the Glu-68 site (the E68R mutation) inverted the channel gating so that it was open in the dark and closed in the light, without altering its ion selectivity. The second mechanism, characterized by fast opening and slow closing of the channel, was not substantially affected by the E68Q mutation, but was controlled by Cys-102. The C102A mutation reduced the rate of channel closing by the second mechanism by ∼100-fold, whereas it had only a twofold effect on the rate of the first. The results show that anion conductance by ACRs has a fundamentally different structural basis than the relatively well studied conductance by cation channelrhodopsins (CCRs), not attributable to simply a modification of the CCR selectivity filter.

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Mao, Rui, and Xiao Li. "Bridging Towers of Multi-task Learning with a Gating Mechanism for Aspect-based Sentiment Analysis and Sequential Metaphor Identification." Proceedings of the AAAI Conference on Artificial Intelligence 35, no. 15 (2021): 13534–42. http://dx.doi.org/10.1609/aaai.v35i15.17596.

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Multi-task learning (MTL) has been widely applied in Natural Language Processing. A major task and its associated auxiliary tasks share the same encoder; hence, an MTL encoder can learn the sharing abstract information between the major and auxiliary tasks. Task-specific towers are then employed upon the sharing encoder to learn task-specific information. Previous works demonstrated that exchanging information between task-specific towers yielded extra gains. This is known as soft-parameter sharing MTL. In this paper, we propose a novel gating mechanism for the bridging of MTL towers. Our method is evaluated based on aspect-based sentiment analysis and sequential metaphor identification tasks. The experiments demonstrate that our method can yield better performance than the baselines on both tasks. Based on the same Transformer backbone, we compare our gating mechanism with other information transformation mechanisms, e.g., cross-stitch, attention and vanilla gating. The experiments show that our method also surpasses these baselines.

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Zhang, Peiran, Chuyi Chen, Xingyu Su, et al. "Acoustic streaming vortices enable contactless, digital control of droplets." Science Advances 6, no. 24 (2020): eaba0606. http://dx.doi.org/10.1126/sciadv.aba0606.

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Advances in lab-on-a-chip technologies are driven by the pursuit of programmable microscale bioreactors or fluidic processors that mimic electronic functionality, scalability, and convenience. However, few fluidic mechanisms allow for basic logic operations on rewritable fluidic paths due to cross-contamination, which leads to random interference between “fluidic bits” or droplets. Here, we introduce a mechanism that allows for contact-free gating of individual droplets based on the scalable features of acoustic streaming vortices (ASVs). By shifting the hydrodynamic equilibrium positions inside interconnected ASVs with multitonal electrical signals, different functions such as controlling the routing and gating of droplets on rewritable fluidic paths are demonstrated with minimal biochemical cross-contamination. Electrical control of this ASV-based mechanism allows for unidirectional routing and active gating behaviors, which can potentially be scaled to functional fluidic processors that can regulate the flow of droplets in a manner similar to the current in transistor arrays.

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Robertson, Kindal M., and D. Peter Tieleman. "Molecular basis of voltage gating of OmpF porin." Biochemistry and Cell Biology 80, no. 5 (2002): 517–23. http://dx.doi.org/10.1139/o02-145.

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OmpF and PhoE from Escherichia coli and related homologous proteins from other Gram-negative bacteria allow the passive transport of small polar molecules across the bacterial outer membrane. In vitro, they exhibit voltage gating depending on the experimental conditions. We review current hypotheses on the underlying molecular mechanism of voltage gating of OmpF porin and show how computer simulations can be used to examine each of the proposed mechanisms. Key words: β-barrels, eyelet region, porins, E. coli, α-haemolysin.

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Akitake, Bradley, Andriy Anishkin, and Sergei Sukharev. "The “Dashpot” Mechanism of Stretch-dependent Gating in MscS." Journal of General Physiology 125, no. 2 (2005): 143–54. http://dx.doi.org/10.1085/jgp.200409198.

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The crystal structure of the small conductance mechanosensitive channel (MscS) has been an invaluable tool in the search for the gating mechanism, however many functional aspects of the channel remain unsettled. Here we characterized the gating of MscS in Escherichia coli spheroplasts in a triple mutant (mscL−, mscS−, mscK−) background. We used a pressure clamp apparatus along with software developed in-lab to generate dose–response curves directly from two-channel recordings of current and pressure. In contrast to previous publications, we found that MscS exhibits essentially voltage-independent activation by tension, but at the same time strong voltage-dependent inactivation under depolarizing conditions. The MscS activation curves obtained under saturating ramps of pressure, at different voltages, gave estimates for the energy, area, and gating charge for the closed-to-open transition as 24 kT, 18 nm2, and +0.8, respectively. The character of activation and inactivation was similar in both K+ and Na+ buffers. Perhaps the most salient and intriguing property of MscS gating was a strong dependence on the rate of pressure application. Patches subjected to various pressure ramps from 2.7 to 240 mmHg/s revealed a midpoint of activation almost independent of rate. However, the resultant channel activity was dramatically lower when pressure was applied slowly, especially at depolarizing pipette voltages. It appears that MscS prefers to respond in full to abrupt stimuli but manages to ignore those applied slowly, as if the gate were connected to the tension-transmitting element via a velocity-sensitive “dashpot.” With slower ramps, channels inactivate during the passage through a narrow region of pressures below the activation midpoint. This property of “dumping” a slowly applied force may be important in environmental situations where rehydration of cells occurs gradually and release of osmolytes is not desirable. MscS often enters the inactivated state through subconducting states favored by depolarizing voltage. The inactivation rate increases exponentially with depolarization. Based on these results we propose a kinetic scheme and gating mechanism to account for the observed phenomenology in the framework of available structural information.

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Li, Shi, Jihe Zhao, Xiao Wang, et al. "Preparation of polyethylene oxide single crystals via liquid gating technology and morphology design strategy." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 77, no. 5 (2021): 819–23. http://dx.doi.org/10.1107/s2052520621008076.

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A novel type of liquid gating technology has been developed to prepare a polyethylene oxide (PEO) single-crystal film, and the crystal growth was observed via atomic force microscopy. The self-seeding method has been widely used in the preparation of polymer single crystals, but the mechanism through which single polymer crystals are formed via the combination of liquid gating technology and the self-seeding method remains unclear. To elucidate the mechanism of this process, a series of experiments were conducted in which a dilute polymer solution was sprayed onto a mica substrate to form a single-crystal film through liquid gating technology to study the effect of the crystallization time on the morphology of a thiol PEO (mPEO-SH) crystal. Based on this research, it was found that liquid gating helps to prevent twinning during crystal growth. The combination of liquid gating and self-seeding technology thus provides a new strategy for polymer single-crystal growth.

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Csanády, László, and Beáta Töröcsik. "Catalyst-like modulation of transition states for CFTR channel opening and closing: New stimulation strategy exploits nonequilibrium gating." Journal of General Physiology 143, no. 2 (2014): 269–87. http://dx.doi.org/10.1085/jgp.201311089.

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Cystic fibrosis transmembrane conductance regulator (CFTR) is the chloride ion channel mutated in cystic fibrosis (CF) patients. It is an ATP-binding cassette protein, and its resulting cyclic nonequilibrium gating mechanism sets it apart from most other ion channels. The most common CF mutation (ΔF508) impairs folding of CFTR but also channel gating, reducing open probability (Po). This gating defect must be addressed to effectively treat CF. Combining single-channel and macroscopic current measurements in inside-out patches, we show here that the two effects of 5-nitro-2-(3-phenylpropylamino)benzoate (NPPB) on CFTR, pore block and gating stimulation, are independent, suggesting action at distinct sites. Furthermore, detailed kinetic analysis revealed that NPPB potently increases Po, also of ΔF508 CFTR, by affecting the stability of gating transition states. This finding is unexpected, because for most ion channels, which gate at equilibrium, altering transition-state stabilities has no effect on Po; rather, agonists usually stimulate by stabilizing open states. Our results highlight how for CFTR, because of its unique cyclic mechanism, gating transition states determine Po and offer strategic targets for potentiator compounds to achieve maximal efficacy.

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Prof. Virendra Umale. "Design and Analysis of Low Power Dual Edge Triggered Mechanism Flip-Flop Employing Power Gating Methodology." International Journal of New Practices in Management and Engineering 6, no. 01 (2020): 26–31. http://dx.doi.org/10.17762/ijnpme.v6i01.53.

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The advancement of battery operated designs has abundantly increases the memory elements and registers to be operated in ultra-low power. That is the this paper we have proposed a design of CT_C DET flip-flop with power gating technique which is the most efficient power consuming reduction technique. The design of the power gating technique involves the pull-up transistor in the Vdd of the circuit and pull-down transistor in the ground terminal. This power gating technique reduces the power consumption by more than 40% than that of the existing design.

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Sánchez-Montañés, Manuel A., Paul F. M. J. Verschure, and Peter König. "Local and Global Gating of Synaptic Plasticity." Neural Computation 12, no. 3 (2000): 519–29. http://dx.doi.org/10.1162/089976600300015682.

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Mechanisms influencing learning in neural networks are usually investigated on either a local or a global scale. The former relates to synaptic processes, the latter to unspecific modulatory systems. Here we study the interaction of a local learning rule that evaluates coincidences of pre- and postsynaptic action potentials and a global modulatory mechanism, such as the action of the basal forebrain onto cortical neurons. The simulations demonstrate that the interaction of these mechanisms leads to a learning rule supporting fast learning rates, stability, and flexibility. Furthermore, the simulations generate two experimentally testable predictions on the dependence of backpropagating action potential on basal forebrain activity and the relative timing of the activity of inhibitory and excitatory neurons in the neocortex.

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Bryant, Sheenah, Tyler Clark, Christopher Thomas, et al. "Insights into the Voltage Regulation Mechanism of the Pore-Forming Toxin Lysenin." Toxins 10, no. 8 (2018): 334. http://dx.doi.org/10.3390/toxins10080334.

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Lysenin, a pore forming toxin (PFT) extracted from Eisenia fetida, inserts voltage-regulated channels into artificial lipid membranes containing sphingomyelin. The voltage-induced gating leads to a strong static hysteresis in conductance, which endows lysenin with molecular memory capabilities. To explain this history-dependent behavior, we hypothesized a gating mechanism that implies the movement of a voltage domain sensor from an aqueous environment into the hydrophobic core of the membrane under the influence of an external electric field. In this work, we employed electrophysiology approaches to investigate the effects of ionic screening elicited by metal cations on the voltage-induced gating and hysteresis in conductance of lysenin channels exposed to oscillatory voltage stimuli. Our experimental data show that screening of the voltage sensor domain strongly affects the voltage regulation only during inactivation (channel closing). In contrast, channel reactivation (reopening) presents a more stable, almost invariant voltage dependency. Additionally, in the presence of anionic Adenosine 5′-triphosphate (ATP), which binds at a different site in the channel’s structure and occludes the conducting pathway, both inactivation and reactivation pathways are significantly affected. Therefore, the movement of the voltage domain sensor into a physically different environment that precludes electrostatically bound ions may be an integral part of the gating mechanism.

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Srinivasan, P., S. Hariharan, P. Manikandan, S. Naveenkumar, N. Harish, and G. Balasubramanian. "Tribological Studies of Shrinkage Defect and Effective Yield Upgrade of Grey Cast-Iron Castings." International Journal for Research in Applied Science and Engineering Technology 10, no. 10 (2022): 1388–96. http://dx.doi.org/10.22214/ijraset.2022.47196.

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Abstract: This study aims to examine the shrinkage flaw in grey cast iron. The poor gating system design, improper composition management, and solid sections with a high modulus (Volume/ Surface area) in the casting are the root causes of the shrinkage fault. The gating mechanism can first be redesigned in order to lessen shrinkage. A new gating system with a different chemical makeup is suggested. Grey cast iron's composition changed due to an increase in carbon content. Thus, proCAST is used to develop and analyze the gating system. Implementing the planned gating system in the foundry served to validate the results. It is accomplished to increase the effective yield

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Li, Lehong, Xuehui Geng, and Peter Drain. "Open State Destabilization by Atp Occupancy Is Mechanism Speeding Burst Exit Underlying KATP Channel Inhibition by Atp." Journal of General Physiology 119, no. 1 (2002): 105–16. http://dx.doi.org/10.1085/jgp.119.1.105.

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The ATP-sensitive potassium (KATP) channel is named after its characteristic inhibition by intracellular ATP. The inhibition is a centerpiece of how the KATP channel sets electrical signaling to the energy state of the cell. In the β cell of the endocrine pancreas, for example, ATP inhibition results from high blood glucose levels and turns on electrical activity leading to insulin release. The underlying gating mechanism (ATP inhibition gating) includes ATP stabilization of closed states, but the action of ATP on the open state of the channel is disputed. The original models of ATP inhibition gating proposed that ATP directly binds the open state, whereas recent models indicate a prerequisite transition from the open to a closed state before ATP binds and inhibits activity. We tested these two classes of models by using kinetic analysis of single-channel currents from the cloned mouse pancreatic KATP channel expressed in Xenopus oocytes. In particular, we combined gating models based on fundamental rate law and burst gating kinetic considerations. The results demonstrate open-state ATP dependence as the major mechanism by which ATP speeds exit from the active burst state underlying inhibition of the KATP channel by ATP.

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Ben-Abu, Yuval. "Potassium Channel Gating Mechanism Modeled by Harmonic Oscillators." Proceedings 2, no. 1 (2018): 9. http://dx.doi.org/10.3390/proceedings2010009.

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Bisset, David, Ben Corry, and Shin-Ho Chung. "The Fast Gating Mechanism in ClC-0 Channels." Biophysical Journal 89, no. 1 (2005): 179–86. http://dx.doi.org/10.1529/biophysj.104.053447.

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Purohit, Prasad, Ananya Mitra, and Anthony Auerbach. "A stepwise mechanism for acetylcholine receptor channel gating." Nature 446, no. 7138 (2007): 930–33. http://dx.doi.org/10.1038/nature05721.

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Zhou, Huan-Xiang, Stanislaw T. Wlodek, and J. Andrew McCammon. "Conformation gating as a mechanism for enzyme specificity." Proceedings of the National Academy of Sciences 95, no. 16 (1998): 9280–83. http://dx.doi.org/10.1073/pnas.95.16.9280.

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Acetylcholinesterase, with an active site located at the bottom of a narrow and deep gorge, provides a striking example of enzymes with buried active sites. Recent molecular dynamics simulations showed that reorientation of five aromatic rings leads to rapid opening and closing of the gate to the active site. In the present study the molecular dynamics trajectory is used to quantitatively analyze the effect of the gate on the substrate binding rate constant. For a 2.4-Å probe modeling acetylcholine, the gate is open only 2.4% of the time, but the quantitative analysis reveals that the substrate binding rate is slowed by merely a factor of 2. We rationalize this result by noting that the substrate, by virtue of Brownian motion, will make repeated attempts to enter the gate each time it is near the gate. If the gate is rapidly switching between the open and closed states, one of these attempts will coincide with an open state, and then the substrate succeeds in entering the gate. However, there is a limit on the extent to which rapid gating dynamics can compensate for the small equilibrium probability of the open state. Thus the gate is effective in reducing the binding rate for a ligand 0.4 Å bulkier by three orders of magnitude. This relationship suggests a mechanism for achieving enzyme specificity without sacrificing efficiency.

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Hoshi, Toshinori. "Mechanism of voltage-dependent gating in potassium channels." Neuroscience Research Supplements 19 (January 1994): S10. http://dx.doi.org/10.1016/0921-8696(94)92294-2.

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Purohit, Prasad G., and Anthony Auerbach. "The Unliganded Gating Mechanism Of Nicotinic Acetylcholine Receptors." Biophysical Journal 96, no. 3 (2009): 166a—167a. http://dx.doi.org/10.1016/j.bpj.2008.12.769.

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