EXTENSIBLE COLLAGEN IN MUSSEL BYSSUS - A NATURAL BLOCK-COPOLYMER

To adhere to solid surfaces, marine mussels produce byssal threads, ea ch of which is a stiff tether at one end and a shock absorber with 160 percent extensibility at the other end. The elastic extensibility of proximal byssus is extraordinary given its construction of collagen an d the limited extension (less than 10 percent) of most collagenous mat erials. From the complementary DNA, we deduced that the primary struct ure of a collagenous protein (preCol-P) predominating in the extensibl e proximal portion of the threads encodes an unprecedented natural blo ck copolymer with three major domain types: a central collagen domain, flanking elastic domains, and histidine-rich terminal domains. The el astic domains have sequence motifs that strongly resemble those of ela stin and the amorphous glycine-rich regions of spider silk fibroins. B yssal thread extensibility may be imparted by the elastic domains of p reCol-P.