Exoskeletal proteins from the crab, Cancer pagurus.

Twelve proteins from calcified regions and five from flexible regions (arthrodial membranes) of the exoskeleton of Cancer pagurus have been purified and sequenced. One of the proteins from calcified exoskeleton is identical to one of the arthrodial membrane proteins. Several of the proteins from the calcified regions resemble proteins from corresponding regions of the exoskeleton of the lobster, Homarus americanus, in containing either two or four copies of an 18-residue sequence motif, which so far has been found only in crustacean calcified exoskeletons. The proteins obtained from the flexible arthrodial membranes resemble the proteins from lobster arthrodial membranes, and the similarities are shared with a number of proteins from flexible cuticles in insects, indicating that the common features in these proteins may be important for the mechanical properties of the materials in which they occur.