Acceptor substrate discrimination in phosphatidyl-myo-inositol mannoside synthesis: structural and mutational analysis of mannosyltransferase Corynebacterium glutamicum PimB'

J Biol Chem. 2010 Nov 26;285(48):37741-52. doi: 10.1074/jbc.M110.165407. Epub 2010 Sep 15.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Corynebacterium glutamicum / chemistry
  • Corynebacterium glutamicum / enzymology*
  • Corynebacterium glutamicum / genetics
  • Crystallography, X-Ray
  • Mannosyltransferases / chemistry*
  • Mannosyltransferases / genetics*
  • Mannosyltransferases / metabolism
  • Mutagenesis, Site-Directed
  • Mutation
  • Phosphatidylinositols / biosynthesis*
  • Substrate Specificity


  • Bacterial Proteins
  • Phosphatidylinositols
  • phosphatidylinositol mannoside
  • Mannosyltransferases

Associated data

  • PDB/3OKA
  • PDB/3OKC
  • PDB/3OKP