Twelve proteins from calcified regions and five from flexible regions (arth
rodial membranes) of the exoskeleton of Cancer pagurus have been purified a
nd sequenced. One of the proteins from calcified exoskeleton is identical t
o one of the arthrodial membrane proteins. Several of the proteins from the
calcified regions resemble proteins from corresponding regions of the exos
keleton of the lobster, Homarus americanus, in containing either two or fou
r copies of an 18-residue sequence motif, which so far has been found only
in crustacean calcified exoskeletons. The proteins obtained from the flexib
le arthrodial membranes resemble the proteins from lobster arthrodial membr
anes, and the similarities are shared with a number of proteins from flexib
le cuticles in insects, indicating that the common features in these protei
ns may be important for the mechanical properties of the materials in which
they occur. (C) 1999 Elsevier Science Inc. All rights reserved.