The Amino-Acid Sequence of the Alkali Light Chains of Rabbit Skeletal-Muscle Myosin

Abstract

The amino-acid sequence of the alkali light chain 1 (A1) of rabbit skeletal muscle myosin has been determined and compared with the sequence of the smaller but related alkali light chain 2 (A2). The molecular weights of the two proteins calculated from these sequence determinations are 20700 and 16500, respectively. The results show that the two proteins have identical sequences over their C-terminal 141 residues. There is an additional sequence of 41 residues at the N-terminal end of A1 which accounts for the extra 4000 molecular weight. Between this additional sequence and the sequence common to both proteins are eight amino-acid residues. Comparison of the sequences of these eight residues in A1 and A2 reveals five amino-acid substitutions. Thus in spite of the very extensive homology between the two proteins, these substitutions indicate that there must be two RNA coding sequences for these light chains in rabbit fast muscle myosin.