Characterization Of Exoskeletal Proteins From The American Lobster, Homarus Americanus

Proteins from the calcified exoskeleton of the lobster, Homarus americanus, were extracted and separated by two-dimensional gel electrophoresis. Electroblotting the proteins onto polyvinylidene difluoride (PVDF) membranes followed by sequence determination gave 16 N-terminal amino acid sequences and revealed that further eight proteins were N-terminally blocked.The relative molecular mass, M-r, was obtained for most of the electrophoretically separated proteins by means of matrix-assisted laser desorption mass spectrometry (MALDIMS) after electroelution from Coomassie-stained two-dimensional polyacrylamide gels.Eleven proteins were purified from extracts of the exoskeleton by low pressure ion exchange chromatography and reversed-phase high performance chromatography, and their sequences were determined by combined use of Edman degradation and mass spectrometry. Good agreement was obtained between the M-r-values measured by mass spectrometry and those calculated from the sequences.Five of the sequenced proteins contain two copies of a previously observed 18-residue sequence motif, while a couple of the remaining sequences show similarity to sequences of exoskeletal proteins from shrimps and spiders. Only limited similarity to insect cuticular proteins was observed. (C) 1998 Elsevier Science Inc.