Sandbox Reserved 381: Difference between revisions

The N terminus of OGT is unusual, consisting of 2.5-13.5 tetratricopeptide repeats (TPRs) depending on alternative splicing.<ref>Kreppel L, Hart G. Regulation of a cytosolic and nuclear O-GlcNAc transferase. Role of the tetratricopeptide repeats. J Biol Chem. 1999;274:32015-32022</ref>Addition of N-acetylglucosamine (GlcNAc) is a ubiquitous form of intracellular glycosylation catalyzed by the conserved O-linked GlcNAc transferase (OGT). The N-terminal domain of tetratricopeptide (TPR) mediates the recognition of a broad range of target proteins. Components of the nuclear pore complex are major OGT targets, as OGT depletion by RNA interference (RNAi) results in the loss of GlcNAc modification at the nuclear envelope. The crystal structure of the homodimeric TPR domain of human OGT, which contains 11.5 TPR repeats gives insight into the mechanism of target recognition. The repeats form an elongated superhelix. The concave surface of the superhelix is lined by absolutely conserved asparagines, in a manner reminiscent of the peptide-binding site of importin alpha. Based on this structural similarity, it is proposed that OGT uses an analogous molecular mechanism to recognize its targets.<ref>PMID:15361863</ref>