A total of six proteins from the abdominal arthrodial membrane (intersegmen
tal membrane) of the lobster, Homarus americanus, were purified and their a
mino acid sequences were determined by a combination of mass spectrometry a
nd Edman degradation. The proteins are acidic with pI-values close to 4 and
they all have molecular masses approximate to 12 kDa. The sequences of fiv
e of the proteins differ in only a few residues, while the sixth protein di
ffers from the others in more than half of the positions. Only little simil
arity is observed between the sequences of the arthrodial membrane proteins
and those of proteins purified from the calcified parts of the exoskeleton
of H. americanus. The arthrodial membrane proteins contain the Rebers-Ridd
iford consensus sequence common in proteins from insect cuticles. Compariso
n of the complete sequences to the sequences available in databases shows t
hat the lobster membrane proteins are more closely related to proteins from
insect pliant cuticles than to proteins derived from cuticles destined for
sclerotization. Characteristic features in the protein sequences are discu
ssed, and it is suggested that the various sequence regions have specific r
oles in determining the mechanical properties of arthrodial membranes. (C)
1998 Elsevier Science Inc. All rights reserved.