title: Barnacle cement: a polymerization model based on evolutionary concepts.
abstract: 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.
authors.affiliation: Duke University Marine Laboratory, Nicholas School of the Environment, Beaufort, NC 28516, USA.
authors.forename: Gary H
authors.initials: GH
authors.lastname: Dickinson
authors.forename: Irving E
authors.initials: IE
authors.lastname: Vega
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Wahl
authors.forename: Beatriz
authors.initials: B
authors.lastname: Orihuela
authors.forename: Veronica
authors.initials: V
authors.lastname: Beyley
authors.forename: Eva N
authors.initials: EN
authors.lastname: Rodriguez
authors.forename: Richard K
authors.initials: RK
authors.lastname: Everett
authors.forename: Joseph
authors.initials: J
authors.lastname: Bonaventura
authors.forename: Daniel
authors.initials: D
authors.lastname: Rittschof
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D006801:Humans; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D008969:Molecular Sequence Data; D011108:Polymers / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D001468:Thoracica / Q000737:chemistry*; D011503:Transglutaminases / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D011108:Polymers; D011506:Proteins; D011503:Transglutaminases; D014357:Trypsin; D002118:Calcium