The sequence of the NH2-terminal 204-residue fragment of the heavy chain of rabbit skeletal muscle myosin.

Abstract

The amino acid sequence of the Mr = 23,000 peptide that is generated by limited tryptic digestion of rabbit skeletal muscle heavy meromyosin was determined. This fragment represents the NH2-terminal 204 residues of the heavy chain of myosin, and its sequence is (formula; see text) This peptide contains the lysine residue (Lys 83) whose reaction with 2,4,6,-trinitrobenzenesulfonate alters the enzymatic activity of myosin, as well as two types of methylated lysines. Position 34 is occupied by epsilon-N-monomethyllysine and lysine in an approximate 60:40 ratio, while position 129 is fully occupied by one of the two epsilon-N-trimethyllysines in myosin heavy chain. There is evidence suggesting that this fragment contains residues that contribute to the ATP-binding site of myosin; the sequence surrounding the epsilon-N-trimethyllysine is devoid of charges and could form a hydrophobic pocket for binding of the adenine moiety while the epsilon-N-trimethyllysine, which carries a positive charge at all pH values, could bind an ATP phosphate group.