It was suggested that CAP-1 might be involved in ACC stabilization in crayfish exoskeleton (7); however, no proof was provided. Indeed, this protein, together with orchestin and GAMP, are considerably different from GAP 65, with the latter lacking an acidic amino acids-rich sequence and possessing different characteristic domains. Protein extracts from the spicules of the sponge Clathrina and the ascidian Pyura pachydermatina have been reported (36, 37) to stabilize synthetic ACCs for up to 3 months. In this study, we demonstrate the capability of crustacean macromolecules to stabilize synthetic ACC. GAP 65 is a purified protein able to stabilize synthetic ACC that remains stable for up to 2 months. The manner by which GAP
65 stabilizes the ACC has yet to be elucidated.