PDBsum entry 4xi9

Transferase

PDB id: 4xi9

Contents

Protein chains

698 a.a.

Ligands

VAL-THR-PRO-VAL-SER-THR-ALA-ALA ×4

12V ×4

References listed in PDB file

Key reference

• Title: The active site of o-Glcnac transferase imposes constraints on substrate sequence.
• Authors: S.Pathak, J.Alonso, M.Schimpl, K.Rafie, D.E.Blair, V.S.Borodkin, A.W.Schüttelkopf, O.Albarbarawi, D.M.Van aalten.
• Ref.: Nat Struct Biol, 2015, 22, 744-750. [DOI no: 10.1038/nsmb.3063]
• PubMed id: 26237509

Abstract

O-GlcNAc transferase (OGT) glycosylates a diverse range of intracellular proteins with O-linked N-acetylglucosamine (O-GlcNAc), an essential and dynamic post-translational modification in metazoans. Although this enzyme modifies hundreds of proteins with O-GlcNAc, it is not understood how OGT achieves substrate specificity. In this study, we describe the application of a high-throughput OGT assay to a library of peptides. We mapped sites of O-GlcNAc modification by electron transfer dissociation MS and found that they correlate with previously detected O-GlcNAc sites. Crystal structures of four acceptor peptides in complex with Homo sapiens OGT suggest that a combination of size and conformational restriction defines sequence specificity in the -3 to +2 subsites. This work reveals that although the N-terminal TPR repeats of OGT may have roles in substrate recognition, the sequence restriction imposed by the peptide-binding site makes a substantial contribution to O-GlcNAc site specificity.