Complete Amino Acid Sequence of Rabbit Muscle Glycogen Phosphorylase

The sequence of the 841 amino acid residues in each subunit (molecular weight 97,412) of rabbit muscle glycogen phosphorylase b (1,4-α -D-glucan:orthophosphate α -glucosyltransferase; EC 2.4.1.1) has been determined. The general strategy was based on limited proteolysis of native phosphorylase b by subtilisin BPN′, yielding two large segments (light and heavy) which were fragmented by cleavage at methionyl-, asparaginyl-glycine, and aspartyl-proline bonds. Analysis of two cyanogen bromide fragments (CB14 and CB17) isolated from the intact molecule yielded the overlap between the light and heavy fragments and the remainder of the sequence. The residues involved in the covalent and allosteric control of the enzyme, and in the binding of the cofactor pyridoxal 5′-phosphate, were identified as serine-14, tyrosine-155, and lysine-679, respectively.