Identification of the 38‐kDa subunit of rabbit skeletal muscle glycogen synthase as glycogenin

Glycogen synthase from rabbit skeletal muscle has been shown to be a complex of two types of subunit which have apparent molecular masses of 86 kDa and 38 kDa and are present in a 1:1 molar ratio. The 38‐kDa component was separatéd from the 86‐kDa catalytic subunit by gel filtration in the presence of 2 M LiBr, and a number of chymotryptic peptides were sequenced. This demonstrated that the 38‐kDa subunit was glycogenin, the protein that is bound covalently to glycogen and believed to be the ‘primer' involved in the initiation of de novo glycogen synthesis.