Primary structure of subfragment-2 from adult chicken cardiac ventricular muscle myosin.

The complete primary structure of the subfragment-2 (S-2) from adult chicken cardiac ventricular muscle myosin has been determined by analysis of peptides derived from digests of S-2 with cyanogen bromide, lysyl endopeptidase, arginyl endopeptidase, and from hydrolysates of CNBr fragments with formic acid. This region composed of 520 amino-acid residues which span the connecting segment between subfragment-1 (S-1) and S-2 to the NH2-terminal portion of light meromyosin (LMM). Comparing this sequence with the partial sequence of the rod from the same chicken ventricular muscle myosin deduced from its nucleotides of cDNA which lacks 64 NH2-terminal amino-acid residues, 14 amino-acid differences and 3 deletion/insertions were recognized. Furthermore, the sequence of S-2 from adult chicken ventricular myosin was compared with corresponding sequences of rat alpha and beta cardiac myosin heavy chains (MHC) and human alpha and beta cardiac MHCs. The results show 83.7%, 82.1%, 83.1% and 82.1% sequence identities, respectively with almost similar degrees of similarities to both alpha- and beta-MHCs. However, sequences of isoform-specific regions in this S-2 from adult chicken ventricular myosin showed clearly a higher homology to those of alpha-MHCs than to beta-MHCs of mammalian cardiac myosins.