O-Linked-N-Acetylglucosamine Transferase (OGT)

O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) catalyzes the addition of a single N-acetylglucosamine in O-glycosidic linkage to serine or threonine residues. Since both phosphorylation and glycosylation compete for similar serine or threonine residues, the two processes may compete for sites, or they may alter the substrate specificity of nearby sites by steric or electrostatic effects. The protein contains nine tetratricopeptide repeats and a putative bipartite nuclear localization signal. The predicted 920-amino acid human protein contains 9 tetratricopeptide repeats and a putative bipartite nuclear localization signal. HeLa cells expressing OGT did not survive well during prolonged incubations, suggesting that this protein may be toxic to the cells. Southern blot analysis indicated that a single OGT gene is present in humans.