Cloning and sequencing of cDNA for akazara scallop tropomyosin

cDNA clones encoding tropomyosin of akazara scallop Chlamys plipponensis ak azara striated adductor muscle were isolated and sequenced. The largest cDN A obtained is composed of 1,995 bp including an open reading frame of 852 ' bp at nucleotide positions 27-878, which deduced amino acid sequence of 284 residues with a calculated molecular weight of 32,540. According to databa se searches on NBRF-PIR 49.0 and GenBank, the amino acid sequence showed hi gher homology of 73% and 700ibto bloodfluke planorb tropomyosin and mussel anterior byssus retractor muscle tropomyosin, respectively, and considerabl y high homology of 53% and 51% to rabbit alpha- and beta-tropomyosins, resp ectively. The sequences corresponding to the critical region for actin-bind ing (residues 1-9) and troponin-T-binding region (near residues 150-180) of rabbit alpha-tropomyosin are conserved also in akazara scallop tropomyosin . As the nine residues at both of the N-terminus and C-terminus are general ly regarded to form a head-to-tail interaction region, the residues at the N-terminus of akazara scallop tropomyosin show high sequence homology to th ose of various muscle tropomyosins. However, those at the C-terminus show l ower sequence homology than those of vertebrate tropomyosin. Thus, head-to- tail interaction of akazara scallop tropomyosin may be different from rabbi t tropomyosin on account of low homology of the C-terminal sequence.