title: Analysis of a new mannosyltransferase required for the synthesis of phosphatidylinositol mannosides and lipoarbinomannan reveals two lipomannan pools in corynebacterineae.
abstract: The cell walls of the Corynebacterineae, which includes the important human pathogen Mycobacterium tuberculosis, contain two major lipopolysaccharides, lipoarabinomannan (LAM) and lipomannan (LM). LAM is assembled on a subpool of phosphatidylinositol mannosides (PIMs), whereas the identity of the LM lipid anchor is less well characterized. In this study we have identified a new gene (Rv2188c in M. tuberculosis and NCgl2106 in Corynebacterium glutamicum) that encodes a mannosyltransferase involved in the synthesis of the early dimannosylated PIM species, acyl-PIM2, and LAM. Disruption of the C. glutamicum NCgl2106 gene resulted in loss of synthesis of AcPIM2 and accumulation of the monomannosylated precursor, AcPIM1. The synthesis of a structurally unrelated mannolipid, Gl-X, was unaffected. The synthesis of AcPIM2 in C. glutamicum DeltaNCgl2106 was restored by complementation with M. tuberculosis Rv2188c. In vivo labeling of the mutant with [3H]Man and in vitro labeling of membranes with GDP-[3H]Man confirmed that NCgl2106/Rv2188c catalyzed the second mannose addition in PIM biosynthesis, a function previously ascribed to PimB/Rv0557. The C. glutamicum Delta NCgl2106 mutant lacked mature LAM but unexpectedly still synthesized the major pool of LM. Biochemical analyses of the LM core indicated that this lipopolysaccharide was assembled on Gl-X. These data suggest that NCgl2106/Rv2188c and the previously studied PimB/Rv0557 transfer mannose residues to distinct mannoglycolipids that act as precursors for LAM and LM, respectively.
authors.affiliation: Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Victorian Bioinformatics Consortium, Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: David J
authors.initials: DJ
authors.lastname: Lea-Smith
authors.forename: Kirstee L
authors.initials: KL
authors.lastname: Martin
authors.forename: James S
authors.initials: JS
authors.lastname: Pyke
authors.forename: Dedreia
authors.initials: D
authors.lastname: Tull
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: McConville
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crellin
mesh_terms: D000595:Amino Acid Sequence; D002473:Cell Wall / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D016695:Glycosyltransferases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry*; D008364:Mannosyltransferases / Q000378:metabolism*; D008954:Models, Biological; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
chemical_list: D008070:Lipopolysaccharides; D010716:Phosphatidylinositols; C050016:lipoarabinomannan; C034154:phosphatidylinositol mannoside; D016695:Glycosyltransferases; D008364:Mannosyltransferases