Auswahl der wissenschaftlichen Literatur zum Thema „Barnacle cement proteins“

Adhesive secretion has a fundamental role in barnacles’ survival, keeping them in an adequate position on the substrate under a variety of hydrologic regimes. It arouses special interest for industrial applications, such as antifouling strategies, underwater industrial and surgical glues, and dental composites. This study was focused on the goose barnacle Pollicipes pollicipes adhesion system, a species that lives in the Eastern Atlantic strongly exposed intertidal rocky shores and cliffs. The protein composition of P. pollicipes cement multicomplex and cement gland was quantitatively studied using a label-free LC-MS high-throughput proteomic analysis, searched against a custom transcriptome-derived database. Overall, 11,755 peptide sequences were identified in the gland while 2880 peptide sequences were detected in the cement, clustered in 1616 and 1568 protein groups, respectively. The gland proteome was dominated by proteins of the muscle, cytoskeleton, and some uncharacterized proteins, while the cement was, for the first time, reported to be composed by nearly 50% of proteins that are not canonical cement proteins, mainly unannotated proteins, chemical cues, and protease inhibitors, among others. Bulk adhesive proteins accounted for one-third of the cement proteome, with CP52k being the most abundant. Some unannotated proteins highly expressed in the proteomes, as well as at the transcriptomic level, showed similar physicochemical properties to the known surface-coupling barnacle adhesive proteins while the function of the others remains to be discovered. New quantitative and qualitative clues are provided to understand the diversity and function of proteins in the cement of stalked barnacles, contributing to the whole adhesion model in Cirripedia.

Barnacles interest the scientific community for multiple reasons: their unique evolutionary trajectory, vast diversity and economic impact—as a harvested food source and also as one of the most prolific macroscopic hard biofouling organisms. A common, yet novel, trait among barnacles is adhesion, which has enabled a sessile adult existence and global colonization of the oceans. Barnacle adhesive is primarily composed of proteins, but knowledge of how the adhesive proteome varies across the tree of life is unknown due to a lack of genomic information. Here, we supplement previous mass spectrometry analyses of barnacle adhesive with recently sequenced genomes to compare the adhesive proteomes of Pollicipes pollicipes (Pedunculata) and Amphibalanus amphitrite (Sessilia). Although both species contain the same broad protein categories, we detail differences that exist between these species. The barnacle-unique cement proteins show the greatest difference between species, although these differences are diminished when amino acid composition and glycosylation potential are considered. By performing an in-depth comparison of the adhesive proteomes of these distantly related barnacle species, we show their similarities and provide a roadmap for future studies examining sequence-specific differences to identify the proteins responsible for functional differences across the barnacle tree of life.

Barnacles represent one of the model organisms used for antifouling research, however, knowledge regarding the molecular mechanisms underlying barnacle cyprid cementation is relatively scarce. Here, RNA-seq was used to obtain the transcriptomes of the cement glands where adhesive is generated and the remaining carcasses of Megabalanus volcano cyprids. Comparative transcriptomic analysis identified 9060 differentially expressed genes, with 4383 upregulated in the cement glands. Four cement proteins, named Mvcp113k, Mvcp130k, Mvcp52k and Mvlcp1-122k, were detected in the cement glands. The salivary secretion pathway was significantly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the differentially expressed genes, implying that the secretion of cyprid adhesive might be analogous to that of saliva. Lysyl oxidase had a higher expression level in the cement glands and was speculated to function in the curing of cyprid adhesive. Furthermore, the KEGG enrichment analysis of the 352 proteins identified in the cement gland proteome partially confirmed the comparative transcriptomic results. These results present insights into the molecular mechanisms underlying the synthesis, secretion and curing of barnacle cyprid adhesive and provide potential molecular targets for the development of environmentally friendly antifouling compounds.

Adhesive proteins of barnacle cement have potential as environmentally friendly adhesives owing to their ability to adhere to various substrates in aqueous environments. By understanding the taxonomic breath of barnacles with different lifestyles, we may uncover commonalities in adhesives produced by these specialized organisms. The 19 kDa cement protein (cp19k) of the stalked barnacle Pollicipes pollicipes was expressed in Escherichia coli BL21 to investigate its adhesive properties. Initial expression of hexahistidine-tagged protein (rPpolcp19k-his) yielded low levels of insoluble protein. Co-overproduction of E. coli molecular chaperones GroEL-GroES and trigger factor (TF) increased soluble protein yields, although TF co-purified with the target protein (TF-rPpolcp19k-his). Surface coat analysis revealed high levels of adsorption of the TF-rPpolcp19k-his complex and of purified E. coli TF on both hydrophobic and hydrophilic surfaces, while low levels of adsorption were observed for rPpolcp19k-his. Tag-free rPpolcp19k protein also exhibited low adsorption compared to fibrinogen and Cell-Tak controls on hydrophobic, neutral hydrophilic and charged self-assembled monolayers under surface plasmon resonance assay conditions designed to mimic the barnacle cement gland or seawater. Because rPpolcp19k protein displays low adhesive capability, this protein is suggested to confer the ability to self-assemble into a plaque within the barnacle cement complex. This article is part of the theme issue ‘Transdisciplinary approaches to the study of adhesion and adhesives in biological systems’.

We focus on the stalked goose barnacle L. anatifera adhesive system, an opportunistic less selective species for the substrate, found attached to a variety of floating objects at seas. Adhesion is an adaptative character in barnacles, ensuring adequate positioning in the habitat for feeding and reproduction. The protein composition of the cement multicomplex and adhesive gland was quantitatively studied using shotgun proteomic analysis. Overall, 11,795 peptide sequences were identified in the gland and 2206 in the cement, clustered in 1689 and 217 proteinGroups, respectively. Cement specific adhesive proteins (CPs), proteases, protease inhibitors, cuticular and structural proteins, chemical cues, and many unannotated proteins were found, among others. In the cement, CPs were the most abundant (80.5%), being the bulk proteins CP100k and -52k the most expressed of all, and CP43k-like the most expressed interfacial protein. Unannotated proteins comprised 4.7% of the cement proteome, ranking several of them among the most highly expressed. Eight of these proteins showed similar physicochemical properties and amino acid composition to known CPs and classified through Principal Components Analysis (PCA) as new CPs. The importance of PCA on the identification of unannotated non-conserved adhesive proteins, whose selective pressure is on their relative amino acid abundance, was demonstrated.

AbstractBarnacle adhesion is a focus for fouling-control technologies as well as the development of bioinspired adhesives, although the mechanisms remain very poorly understood. The barnacle cypris larva is responsible for surface colonisation. Cyprids release cement from paired glands that contain proteins, carbohydrates and lipids, although further compositional details are scant. Several genes coding for cement gland-specific proteins were identified, but only one of these showed database homology. This was a lysyl oxidase-like protein (lcp_LOX). LOX-like enzymes have been previously identified in the proteome of adult barnacle cement secretory tissue. We attempted to produce recombinant LOX in E. coli, in order to identify its role in cyprid cement polymerisation. We also produced two other cement gland proteins (lcp3_36k_3B8 and lcp2_57k_2F5). lcp2_57k_2F5 contained 56 lysine residues and constituted a plausible substrate for LOX. While significant quantities of soluble lcp3_36k_3B8 and lcp2_57k_2F5 were produced in E. coli, production of stably soluble lcp_LOX failed. A commercially sourced human LOX catalysed the crosslinking of lcp2_57k_2F5 into putative dimers and trimers, and this reaction was inhibited by lcp3_36k_3B8. Inhibition of the lcp_LOX:lcp2_57k_2F5 reaction by lcp3_36k_3B8 appeared to be substrate specific, with no inhibitory effect on the oxidation of cadaverine by LOX. The results demonstrate a possible curing mechanism for barnacle cyprid cement and, thus, provide a basis for a more complete understanding of larval adhesion for targeted control of marine biofouling and adhesives for niche applications.

Solidified adhesive (cement) of three balanid barnacles (Crustacea: Cirripedia) was dissolved using different concentrations of sodium dodecyl sulphate containing a reducing agent. The proteins were separated using SDS-PAGE and blotted onto polyvinylidene difluoride membrane for sequencing. Commonly occurring bands in the cement of each species were identified. One particular protein of 39 kD, found in the cement of Balanus perforatus, has the following N-terminal sequence: TYFPVLSYG?SSSLAPVI, where the? is most likely cysteine. Quinones were not identified in the cement by either infra-red, ultraviolet-visible or solid-state nuclear magnetic resonance spectroscopy and the successful dissolution and sequencing of cement proteins mitigates against their presence. Cement contains a mixture of highly hydrophobic proteins which are cross-linked through cysteine residues. It is the combination of these two components which makes cement highly resistant to chemical degradation. As a result bacteria are usually absent from the cement, possibly further excluded from the porous core of the cement by its smooth outer crust.

Barnacle cement is an underwater adhesive that is used for permanent settlement, and is an insoluble protein complex. A method for rendering soluble the cement of Megabalanus rosa has been developed, and three major proteins have been identified in a previous study. To survey the M. rosa cement proteins in a lower molecular mass range, the cement proteins were separated by reversed-phase HPLC and a previously unidentified protein named 20kDa M. rosa cement protein (Mrcp-20k) was found. Mrcp-20k cDNA was cloned to reveal its primary structure. This cDNA was 902bp long and encoded a 202 amino acid-long open reading frame, including 19 amino acids of the signal sequence. The molecular mass in the disulphide form was calculated to be 20357Da and the isoelectric point of the mature polypeptide was 4.72. Mrcp-20k was characterized by an abundance of Cys residues and charged amino acids. The most common amino acid was Cys (17.5%), with Asp (11.5%), Glu (10.4%) and His (10.4%) following in order of magnitude. The alignment of the Cys residues indicated the primary structure of this protein to consist of six degenerated repeats, each about 30 residues long. Mrcp-20k has no intermolecular disulphide bonds and no free thiol groups of Cys in the insoluble cement complex. Abundant Cys is thought to play a role in maintaining the topology of charged amino acids on the molecular surface by intramolecular disulphide-bond formation. The possible function of abundant charged amino acids, including the interaction with a variety of surface metals on the substratum, is discussed.

Les balanes adhèrent de manière robuste et permanente à divers substrats sous-marins grâce à de fortes interactions d’une couche complexe multiprotéique appelée « ciment ». Cependant, les interactions intermoléculaires responsables des fortes propriétés adhésives du ciment de bernacle restent mal comprises. Une hypothèse centrale de cette thèse est que les propriétés sous-marines du complexe cimentier sont intimement liées aux caractéristiques moléculaires des protéines de ciment (CP) formant le complexe de ciment. Des études antérieures ont montré que le ciment est fait de nanofibrilles de type amyloïde qui peuvent contribuer à l’adhérence. Cependant, la protéine responsable de la formation de ces nanofibrilles reste inconnue. Dans cette étude, les caractéristiques morphologiques à l’échelle nanométrique des protéines de ciment recombinantes (CP) de la balane Megabalanus rosa (MrCP19 et MrCP20, avec les chiffres indiquant un poids moléculaire de 19 kDa et 20 kDa respectivement) ont été caractérisées par la mesure du dichroïsme circulaire (CD), le test Thioflavin T (ThT), la microscopie à force atomique (AFM) et la microscopie électronique à transmission (TEM), suggérant le potentiel de former des structures nano-fibrillaires dans certaines conditions. Sur la base de la structure primaire et de la morphologie de surface des protéines, des études mécaniques, biochimiques et antimicrobiennes ont été menées pour comprendre les rôles uniques de ces protéines interfaciales sur la croissance des balanes et le processus d’attachement à la surface, par exemple la biominéralisation et le contrôle de la biodégradation. Les mesures effectuées à l’aide de l’appareil de force de surface (SFA) et de la microbalance à cristaux de quartz avec surveillance de la dissipation (QCM-D) ont montré que les interactions électrostatiques jouent un rôle clé dans l’adsorption et l’adhésion de surface de MrCP19 et MrCP20. En outre, l’influence mutuelle de la croissance de la plaque de base de bernacle (minéralisation de carbonate de calcium) et de la fibrillation de la protéine de ciment MrCP20 adjacente a été étudiée à l’aide de surfaces d’or fonctionnalisées monocouches (SAM) auto-assemblées, de spectroscopie Raman, de QCM-D, de spectromètre photoélectronique à rayons X (XPS) et de spectroscopie infrarouge à transformée de Fourier à réflectance totale atténuée (ATR-FTIR). Parallèlement, l’influence du substrat externe adjacent à la protéine de ciment MrCP19 sur les cellules bactériennes présentes dans le biofilm sur les surfaces sous-marines en milieu marin a été démontrée à l’aide de différents tests microbiologiques, notamment le test de zone d’inhibition, le test de concentration minimale inhibitrice (CMI), la MET, l’étude de fluorescence, etc. Plus intéressant encore, une hypothèse intrigante concernant le processus de fibrillation amyloïde et l’activité antimicrobienne a été suggérée. Sur la base de ces examens préliminaires, les deux PC interfaciaux ont montré des responsabilités potentielles distinctes sur le tassement des bernacles, non seulement avec son adhérence, mais aussi avec d’autres rôles fonctionnels aux interfaces. Ces travaux amélioreront nos connaissances sur les contributions individuelles de MrCP19 et MrCP20 dans le complexe cimentier et donc dans la capacité globale d’adhésion sous-marine des balanes. À cet égard, la thèse vise à fournir des lignes directrices moléculaires pour le développement de mimiques polymères inspirés des PC (à base de peptides ou de protéines) à partir de ce système moléculaire bio-adhésif
Barnacles adhere themselves robustly and permanently to diverse underwater substrates through strong interactions of a multi-protein complex layer called the “cement”. However, the intermolecular interactions responsible for the strong adhesive properties of the barnacle cement remains poorly understood. A central hypothesis of this thesis is that underwater properties of the cement complex are intimately linked to the molecular characteristics of cement proteins (CPs) forming the cement complex. Previous studies have shown that the cement is made of amyloid-like nanofibrils that may contribute to adhesion. However, the protein responsible for the formation of these nanofibrils remain unknown. In this study, the nanoscale morphological features of recombinant cement proteins (CPs) from the barnacle Megabalanus rosa (MrCP19 and MrCP20, with the numbers indicating molecular weight of 19 kDa and 20 kDa respectively) were characterized by Circular Dichroism (CD) measurement, Thioflavin T (ThT) assay, Atomic Force Microscopy (AFM), and Transmission Electron Microscopy (TEM), suggesting the potential to form nano-fibrillar structures under certain conditions. Based on the proteins’ primary structure and surface morphology, mechanical, biochemical, and antimicrobial studies were conducted to understand the unique roles of these interfacial proteins on barnacle growth and surface attachment process, for instance biomineralization and biodegradation control. Measurements using Surface Force Apparatus (SFA) and Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) illustrated that electrostatic interactions play a key role in surface adsorption and adhesion of MrCP19 and MrCP20. In addition, the mutual influence of barnacle base plate growth (calcium carbonate mineralization) and the adjacent cement protein MrCP20 fibrillation was investigated using self-assembled monolayer (SAM) functionalized gold surfaces, Raman spectroscopy, QCM-D, X-ray photoelectron spectrometer (XPS), and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Concurrently, the influence of the external substrate adjacent cement protein MrCP19 on bacteria cells which are present in biofilm on underwater surfaces in marine environment was demonstrated using different microbiology tests including zone of inhibition test, Minimum inhibitory concentration (MIC) assay, TEM, fluorescence study, and so on. More interestingly, an intriguing hypothesis regarding amyloid fibrillation process and antimicrobial activity was suggested. Based on these preliminary examinations, the two interfacial CPs showed distinctive potential responsibilities on barnacle settlement not only with its adhesion but also with other functional roles at the interfaces. This work will improve our knowledge about individual contributions of MrCP19 and MrCP20 in cement complex and hence in overall underwater adhesion capacity of barnacles. In this regard, the thesis aims at providing molecular guidelines towards the development of CPs inspired polymeric (peptide or protein based) mimics from this bio-adhesive molecular system

Enzymes and biochemical mechanisms essential to survival are under extreme selective pressure and are highly conserved through evolutionary time. We applied this evolutionary concept to barnacle cement polymerization, a process critical to barnacle fitness that involves aggregation and cross-linking of proteins. The biochemical mechanisms of cement polymerization remain largely unknown. We hypothesized that this process is biochemically similar to blood clotting, a critical physiological response that is also based on aggregation and cross-linking of proteins. Like key elements of vertebrate and invertebrate blood clotting, barnacle cement polymerization was shown to involve proteolytic activation of enzymes and structural precursors, transglutaminase cross-linking and assembly of fibrous proteins. Proteolytic activation of structural proteins maximizes the potential for bonding interactions with other proteins and with the surface. Transglutaminase cross-linking reinforces cement integrity. Remarkably, epitopes and sequences homologous to bovine trypsin and human transglutaminase were identified in barnacle cement with tandem mass spectrometry and/or western blotting. Akin to blood clotting, the peptides generated during proteolytic activation functioned as signal molecules, linking a molecular level event (protein aggregation) to a behavioral response (barnacle larval settlement). Our results draw attention to a highly conserved protein polymerization mechanism and shed light on a long-standing biochemical puzzle. We suggest that barnacle cement polymerization is a specialized form of wound healing. The polymerization mechanism common between barnacle cement and blood may be a theme for many marine animal glues.
Dissertation