Phosphorylation of K-casein by glycogen synthase kinase-3 from rabbit skeletal muscle.
Glycogen synthase kinase-3 (ATP:protein phosphotransferase, EC 2.7.1.37) phosphorylated K-casein 20-fold more rapidly than beta-casein, while alpha S1-casein was not a substrate. This distinguished it from casein kinase-I and casein kinase-II, which phosphorylate the beta-casein variant preferentially. Glycogen synthase kinase-3 phosphorylated a serine residue(s) in the C-terminal cyanogen bromide fragment on K-casein. In contrast, cyclic AMP-dependent protein kinase phosphorylated the N-terminal fragment, and phosphorylase kinase the N-terminal and intermediate cyanogen bromide fragments. The results emphasize the potential value of casein phosphorylation as a means of classifying protein kinases.
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002364:Caseins / Q000378:metabolism*; D003488:Cyanogen Bromide; D038341:Glycogen Synthase Kinases; D009132:Muscles / Q000201:enzymology*; D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits
D002364:Caseins; D010446:Peptide Fragments; D011494:Protein Kinases; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D003488:Cyanogen Bromide