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Structure of the Pmt3-MIR domain with bound ligands
Structural highlights
FunctionPMT3_YEAST Protein O-mannosyltransferase involved in O-glycosylation which is essential for cell wall rigidity. Forms a heterodimeric complex with PMT5 and more rarely with PMT1 to transfer mannose from Dol-P-mannose to Ser or Thr residues on proteins. Seems to have redundant activity to PMT2.[1] Publication Abstract from PubMedProtein O-mannosyltransferases (PMTs) represent a conserved family of multispanning endoplasmic reticulum membrane proteins involved in glycosylation of S/T-rich protein substrates and unfolded proteins. PMTs work as dimers and contain a luminal MIR domain with a beta-trefoil fold, which is susceptive for missense mutations causing alpha-dystroglycanopathies in humans. Here, we analyze PMT-MIR domains by an integrated structural biology approach using X-ray crystallography and NMR spectroscopy and evaluate their role in PMT function in vivo. We determine Pmt2- and Pmt3-MIR domain structures and identify two conserved mannose-binding sites, which are consistent with general beta-trefoil carbohydrate-binding sites (alpha, beta), and also a unique PMT2-subfamily exposed FKR motif. We show that conserved residues in site alpha influence enzyme processivity of the Pmt1-Pmt2 heterodimer in vivo. Integration of the data into the context of a Pmt1-Pmt2 structure and comparison with homologous beta-trefoil - carbohydrate complexes allows for a functional description of MIR domains in protein O-mannosylation. Functional implications of MIR domains in protein O-mannosylation.,Chiapparino A, Grbavac A, Jonker HR, Hackmann Y, Mortensen S, Zatorska E, Schott A, Stier G, Saxena K, Wild K, Schwalbe H, Strahl S, Sinning I Elife. 2020 Dec 24;9. pii: 61189. doi: 10.7554/eLife.61189. PMID:33357379[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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