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Acceptor Substrate Discrimination in Phosphatidyl-myo-inositol Mannoside Synthesis

By S.M Batt, Talat Jabeen, Arun K. Mishra, Natacha Veerapen, Karin Krumbach, Lothar Eggeling, Gurdyal S Besra and K. Futterer

Abstract

Long term survival of the pathogen Mycobacterium tuberculosis in humans is linked to the immunomodulatory potential of its complex cell wall glycolipids, which include the phosphatidylinositol mannoside (PIM) series as well as the related lipomannan and lipoarabinomannan glycoconjugates. PIM biosynthesis is initiated by a set of cytosolic α-mannosyltransferases, catalyzing glycosyl transfer from the activated saccharide donor GDP-α-d-mannopyranose to the acceptor phosphatidyl-myo-inositol (PI) in an ordered and regio-specific fashion. Herein, we report the crystal structure of mannosyltransferase Corynebacterium glutamicum PimB′ in complex with nucleotide to a resolution of 2.0 Å. PimB′ attaches mannosyl selectively to the 6-OH of the inositol moiety of PI. Two crystal forms and GDP- versus GDP-α-d-mannopyranose-bound complexes reveal flexibility of the nucleotide conformation as well as of the structural framework of the active site. Structural comparison, docking of the saccharide acceptor, and site-directed mutagenesis pin regio-selectivity to a conserved Asp residue in the N-terminal domain that forces presentation of the correct inositol hydroxyl to the saccharide donor

Topics: QP Physiology
Publisher: American Society for Biochemistry and Molecular Biology
Year: 2010
OAI identifier: oai:eprints.bham.ac.uk:585

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