6pxu
Crystal structure of human GalNAc-T12 bound to a diglycosylated peptide, Mn2+, and UDP
Structural highlights
DiseaseGLT12_HUMAN Disease susceptibility is associated with variations affecting the gene represented in this entry. The role of GALNT12 in colon cancer susceptibility is however subject to discussion: studies on 103 probants with colorectal cancer 1 (CRCS1) suggest that it does not act as a major contributor of CRCS1 (PubMed:24115450).[1] FunctionGLT12_HUMAN Catalyzes the initial reaction in O-linked oligosaccharide biosynthesis, the transfer of an N-acetyl-D-galactosamine residue to a serine or threonine residue on the protein receptor. Has activity toward non-glycosylated peptides such as Muc5AC, Muc1a and EA2, and no detectable activity with Muc2 and Muc7. Displays enzymatic activity toward the Gal-NAc-Muc5AC glycopeptide, but no detectable activity to mono-GalNAc-glycosylated Muc1a, Muc2, Muc7 and EA2. May play an important role in the initial step of mucin-type oligosaccharide biosynthesis in digestive organs. Publication Abstract from PubMedPolypeptide N-acetylgalactosaminyl transferases (GalNAc-Ts) initiate mucin type O-glycosylation by catalyzing the transfer of N-acetylgalactosamine (GalNAc) to Ser or Thr on a protein substrate. Inactive and partially active variants of the isoenzyme GalNAc-T12 are present in subsets of patients with colorectal cancer, and several of these variants alter nonconserved residues with unknown functions. While previous biochemical studies have demonstrated that GalNAc-T12 selects for peptide and glycopeptide substrates through unique interactions with its catalytic and lectin domains, the molecular basis for this distinct substrate selectivity remains elusive. Here we examine the molecular basis of the activity and substrate selectivity of GalNAc-T12. The X-ray crystal structure of GalNAc-T12 in complex with a di-glycosylated peptide substrate reveals how a nonconserved GalNAc binding pocket in the GalNAc-T12 catalytic domain dictates its unique substrate selectivity. In addition, the structure provides insight into how colorectal cancer mutations disrupt the activity of GalNAc-T12 and illustrates how the rules dictating GalNAc-T12 function are distinct from those for other GalNAc-Ts. The structure of the colorectal cancer-associated enzyme GalNAc-T12 reveals how nonconserved residues dictate its function.,Fernandez AJ, Daniel EJP, Mahajan SP, Gray JJ, Gerken TA, Tabak LA, Samara NL Proc Natl Acad Sci U S A. 2019 Oct 8;116(41):20404-20410. doi:, 10.1073/pnas.1902211116. Epub 2019 Sep 23. PMID:31548401[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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