Sequence of the carboxyl-terminal 492 residues of rabbit muscle glycogen phosphorylase including the pyridoxal 5'-phosphate binding site.

This communication presents the strategy and experimental details which establish the amino acid sequence of the carboxyl-terminal 492 residues (residues 350 through 841) of rabbit muscle glycogen phosphorylase (EC 2.4.1.1). The heavy segment (Hs), derived from the native enzyme by limited proteolysis with subtilisin, was cleaved with cyanogen bromide to yield 15 fragments. The amino acid sequences of 12 of these are described herein. The sequence of 3 other fragments (CB17C, CB18, and CB15) is described in accompanying reports by Koide, A., et al., and Hermann, j., et al. ((1978) Biochemistry 17 (first and second papers, respectively, in a series in this issue)). These 15 fragments were aligned by analysis of three others generated by cleavage of the heavy segment Hs at asparaginylglycine bonds with hydroxylamine and of four more generated by acid cleavage of aspartylproline bonds. Lysine-679 was identified as the binding site of the essential cofactor pyridoxal 5'-phosphate. These data, together with those reported in the accompanying papers (vide supra), establish the complete sequence of the 841 amino acid residues in glycogen phosphorylase. They provide a chemical basis on which the relationship between structure and function of the enzyme can be examined.