The peculiar collagens of mussel byssus.
The byssal collagens of marine mussels are extracorporeal collagens that function in byssal threads under tension. Each byssal thread resembles a shock absorber in its mechanical design: it is strong and stiff at one end and pliably elastic at the other. Primary structures of three of these collagens (preCols), deduced from cDNAs, reveal signal peptide sequences, but no N-glycosylation sites or propeptides typical of procollagens. The collagen domain (40-50 kDa) represents roughly half the mass of the mature molecules and is distinguished by its central location, abundant Gly-Gly-X repeats, and "flaws" (usually Gly deletions). Flanking the collagen domains on both sides are structural domains that resemble elastin in preCol-P, spider drag-line silk in preCol-D, and Gly-rich cell wall proteins in preCol-NG. Not surprisingly, studies of preCol distribution in byssal threads suggest preCol-P enhancement in the elastic proximal portion, while preCol-D predominates in the stiffer distal portion. PreCol-NG, in contrast, is evenly distributed. Although no data are yet available on the fibrillogenesis and cross-linking of the preCols, the quarter-stagger assembly of fibrillar interstitial collagens does not pertain since preCols lack the terminal peptides of tropocollagen. Metal-binding by histidines may mediate the initial inter- and intramolecular stabilization of preCols in the byssus.
Department of Chemistry and Biochemistry, University of Delaware, Newark 19716, USA.
J H
JH
Waite
X X
XX
Qin
K J
KJ
Coyne
D000818:Animals; D001483:Base Sequence; D003094:Collagen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003432:Cross-Linking Reagents; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism*
D003432:Cross-Linking Reagents; D003094:Collagen