Characterization of proteins from arthrodial membranes of the lobster, Homarus americanus

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.