Abstract
Mycobacterium tuberculosis (M. tb) pathogenesis involves the interaction between the mycobacterial cell envelope and host macrophage, a process mediated, in part, by binding of the mannose caps of M. tb lipoarabinomannan (ManLAM) to the macrophage mannose receptor (MR). A presumed critical step in the biosynthesis of ManLAM, and other mannose-containing glycoconjugates, is the conversion of mannose-6-phosphate to mannose-1-phosphate, by a phosphomannomutase (PMM), to produce GDP-mannose, the primary mannose-donor in mycobacteria. We have identified four M. tb H37Rv genes with similarity to known PMMs. Using in vivo complementation of PMM and phosphoglucomutase (PGM) deficient strains of Pseudomonas aeruginosa, and an in vitro enzyme assay, we have identified both PMM and PGM activity from one of these genes, Rv3257c (MtmanB). MtmanB overexpression in M. smegmatis produced increased levels of LAM, lipomannan, and phosphatidylinositol mannosides (PIMs) compared with control strains and led to a 13.3 +/- 3.9-fold greater association of mycobacteria with human macrophages, in a mannan-inhibitable fashion. This increased association was mediated by the overproduction of higher order PIMs that possess mannose cap structures. We conclude that MtmanB encodes a functional PMM involved in the biosynthesis of mannosylated lipoglycans that participate in the association of mycobacteria with macrophage phagocytic receptors.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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Carbohydrate Conformation
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Carbohydrate Sequence
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Cell Wall / chemistry
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Gene Expression Regulation, Bacterial
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Genetic Complementation Test
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Humans
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Lectins, C-Type / metabolism
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Lipopolysaccharides / chemistry
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Lipopolysaccharides / metabolism
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Macrophages / metabolism
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Macrophages / microbiology*
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Mannose Receptor
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Mannose-6-Phosphate Isomerase / genetics
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Mannose-6-Phosphate Isomerase / metabolism*
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Mannose-Binding Lectins / metabolism
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Molecular Sequence Data
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Molecular Structure
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Multienzyme Complexes / genetics
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Multienzyme Complexes / metabolism*
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Mycobacterium smegmatis / cytology
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Mycobacterium smegmatis / genetics
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Mycobacterium smegmatis / metabolism*
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Mycobacterium tuberculosis / enzymology*
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Mycobacterium tuberculosis / genetics
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Nucleotidyltransferases / genetics
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Nucleotidyltransferases / metabolism*
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Open Reading Frames
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Phosphatidylinositols / biosynthesis*
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Phosphatidylinositols / chemistry
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Phosphotransferases (Phosphomutases) / genetics
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Phosphotransferases (Phosphomutases) / metabolism*
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Pseudomonas aeruginosa / genetics
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Pseudomonas aeruginosa / metabolism
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Receptors, Cell Surface / metabolism
Substances
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Bacterial Proteins
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Lectins, C-Type
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Lipopolysaccharides
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Mannose Receptor
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Mannose-Binding Lectins
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Multienzyme Complexes
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Phosphatidylinositols
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Receptors, Cell Surface
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lipoarabinomannan
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lipomannan
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phosphatidylinositol mannoside
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ManB protein, bacteria
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Nucleotidyltransferases
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Mannose-6-Phosphate Isomerase
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Phosphotransferases (Phosphomutases)
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phosphomannomutase