Structure of an O-GlcNAc transferase homolog provides insight into intracellular glycosylation

N-Acetylglucosamine (O-GlcNAc) modification of proteins provides a mechanism for the control of diverse cellular processes through a dynamic interplay with phosphorylation. UDP-GlcNAc:polypeptidyl transferase (OGT) catalyzes O-GlcNAc addition. The structure of an intact OGT homolog and kinetic analysis of human OGT variants reveal a contiguous superhelical groove that directs substrates to the active site.