KIM, H.-W.; YU, X.-L.; MYKLES, D.L.: Characterization of cDNAs encoding calpain genes expressed in lobster muscles

Calpains constitute a diverse family of calcium-dependent cyteine proteinases in animal cells (83 calpain genes have been reported in 23 species). In decapod crustaceans, four calpain activities mediate molt-induced claw muscle atrophy. Selective degradation of myofibrillar proteins reduces muscle mass by as much as 78% so that the claws are easily withdrawn during ecdysis. cDNA libraries synthesized from American lobster (Homarus americanus) claw muscle mRNA were screened for calpain genes using PCR in combination with primers to highly conserved sequences in the catalytic domain (Domain II). In addition to a muscle-specific calpain (Ha-CalpM; Yu, X.-L. & Mykles,D.L., Am. Zool. 40:1270), two cDNAs encoding partial sequences were isolated. The DNA sequence of clone C4 (593 bp) was 98% identical to that of a Drosophila calpain (Dm-CalpA). The DNA sequence of clone C5 (705 bp) was 89% identical to Ha-CalpM. Our goal is to obtain full-length sequences of both genes using 3� and 5� RACE and to determine their pattern of expression during the intermolt cycle. Supported by NSF (IBN-9904528).