title: The pimB gene of Mycobacterium tuberculosis encodes a mannosyltransferase involved in lipoarabinomannan biosynthesis.
abstract: The biosynthesis of lipoarabinomannan (LAM), a key mycobacterial lipoglycan that has been implicated in numerous immunoregulatory functions, was examined utilizing D-mannosamine (ManN) as a tool to identify mannosyltransferase genes involved in LAM synthesis. Cell-free reactions utilizing cellular membranes of mycobacteria as the enzyme source indicated that ManN inhibited the synthesis of phosphatidylinositol mannosides, early precursors to LAM. A selection strategy was devised to screen a Mycobacterium tuberculosis genomic library in Mycobacterium smegmatis for clones conferring conditional resistance to ManN, with the rationale that overexpression of the gene(s) encoding a target of ManN would impart a ManN-resistant phenotype under these conditions. This strategy led to the identification of pimB, whose deduced amino acid sequence shows similarity to mannosyltransferases and other glycosyltransferases. Partially purified recombinant PimB protein from Escherichia coli or membranes from M. smegmatis overexpressing the pimB gene were used in cell-free assays to show that PimB catalyzes the formation of triacylphosphatidylinositol dimannoside from GDP-mannose and triacylphosphatidylinositol monomannoside.
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Schaeffer
authors.forename: K H
authors.initials: KH
authors.lastname: Khoo
authors.forename: G S
authors.initials: GS
authors.lastname: Besra
authors.forename: D
authors.initials: D
authors.lastname: Chatterjee
authors.forename: P J
authors.initials: PJ
authors.lastname: Brennan
authors.forename: J T
authors.initials: JT
authors.lastname: Belisle
authors.forename: J M
authors.initials: JM
authors.lastname: Inamine
mesh_terms: D001426:Bacterial Proteins; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D015698:Genomic Library; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D006595:Hexosamines / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D008362:Mannosides / Q000378:metabolism; D008364:Mannosyltransferases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology / Q000235:genetics*; D010716:Phosphatidylinositols / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012641:Selection, Genetic; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D001426:Bacterial Proteins; D006595:Hexosamines; D008070:Lipopolysaccharides; D008362:Mannosides; D010716:Phosphatidylinositols; D011994:Recombinant Proteins; C050016:lipoarabinomannan; C054977:phosphatidylinositol dimannoside; C034154:phosphatidylinositol mannoside; C008322:mannosamine; D006155:Guanosine Diphosphate Mannose; D008364:Mannosyltransferases; C400532:PimB protein, Mycobacterium tuberculosis