cDNA cloning of myosin rod and the complete primary structure of myosin heavy chain of walleye pollack fast skeletal muscle

The amino acid sequences of myosin rod containing subfragment-2 (S2) and light meromyosin (LMM) were determined by cDNA cloning for walleye pollack fast skeletal myosin heavy chain. While S2 and LMM were composed of 442 and 656 amino acid residues, a total of 1937 amino acid residues accounted for the whole myosin heavy chain molecule with previously determined sequence for the subfragment-1 heavy chain region of this fish. Both regions for S2 and LMM showed a seven-residue repeat pattern characteristic to fibrous proteins with a coiled-coil structure of two α-helices, displaying a, b, c, d, e, f, and g where positions a and d were frequently occupied by hydrophobic amino acids and c and g often contained charged residues. The occurrence of a 28-residue unit with repetitive sequence was also strongly suggested, when one and three skip residues were adopted into S2 and LMM, respectively. Thus, walleye pollack S2 and LMM consisted of 17 and 24 zones with a 28-residue repeat rearrangement. There were several amino acid substitutions which might account for a low thermal stability of walleye pollack myosin heavy chain in comparison with the sequences of higher vertebrate counterparts. However, it seemed difficult to interpret such low stability only from the comparison in the 28-residue repeat arrangement at the primary structure.