@article {691,
	title = {Mutations in pimE restore lipoarabinomannan synthesis and growth in a Mycobacterium smegmatis lpqW mutant.},
	journal = {J Bacteriol},
	volume = {190},
	year = {2008},
	month = {2008 May},
	pages = {3690-9},
	abstract = {Lipoarabinomannans (LAMs) and phosphatidylinositol mannosides (PIMs) are abundant glycolipids in the cell walls of all corynebacteria and mycobacteria, including the devastating human pathogen Mycobacterium tuberculosis. We have recently shown that M. smegmatis mutants of the lipoprotein-encoding lpqW gene have a profound defect in LAM biosynthesis. When these mutants are cultured in complex medium, spontaneous bypass mutants consistently evolve in which LAM biosynthesis is restored at the expense of polar PIM synthesis. Here we show that restoration of LAM biosynthesis in the lpqW mutant results from secondary mutations in the pimE gene. PimE is a mannosyltransferase involved in converting AcPIM4, a proposed branch point intermediate in the PIM and LAM biosynthetic pathways, to more polar PIMs. Mutations in pimE arose due to insertion of the mobile genetic element ISMsm1 and independent point mutations that were clustered in predicted extracytoplasmic loops of this polytopic membrane protein. Our findings provide the first strong evidence that LpqW is required to channel intermediates such as AcPIM4 into LAM synthesis and that loss of PimE function results in the accumulation of AcPIM4, bypassing the need for LpqW. These data highlight new mechanisms regulating the biosynthetic pathways of these essential cell wall components.},
	keywords = {Cell Wall, Lipopolysaccharides, Lipoproteins, Mannosyltransferases, Mutation, Mycobacterium smegmatis, Phosphatidylinositols},
	issn = {1098-5530},
	doi = {10.1128/JB.00200-08},
	author = {Crellin, Paul K and Kovacevic, Svetozar and Martin, Kirstee L and Brammananth, Rajini and Morita, Yasu S and Billman-Jacobe, Helen and McConville, Malcolm J and Coppel, Ross L}
}
@article {694,
	title = {Identification of a novel protein with a role in lipoarabinomannan biosynthesis in mycobacteria.},
	journal = {J Biol Chem},
	volume = {281},
	year = {2006},
	month = {2006 Apr 7},
	pages = {9011-7},
	abstract = {All species of Mycobacteria synthesize distinctive cell walls that are rich in phosphatidylinositol mannosides (PIMs), lipomannan (LM), and lipoarabinomannan (LAM). PIM glycolipids, having 2-4 mannose residues, can either be channeled into polar PIM species (with 6 Man residues) or hypermannosylated to form LM and LAM. In this study, we have identified a Mycobacterium smegmatis gene, termed lpqW, that is required for the conversion of PIMs to LAM and is highly conserved in all mycobacteria. A transposon mutant, Myco481, containing an insertion near the 3{\textquoteright} end of lpqW exhibited altered colony morphology on complex agar medium. This mutant was unstable and was consistently overgrown by a second mutant, represented by Myco481.1, that had normal growth and colony characteristics. Biochemical analysis and metabolic labeling studies showed that Myco481 synthesized the complete spectrum of apolar and polar PIMs but was unable to make LAM. LAM biosynthesis was restored to near wild type levels in Myco481.1. However, this mutant was unable to synthesize the major polar PIM (AcPIM6) and accumulated a smaller intermediate, AcPIM4. Targeted disruption of the lpqW gene and complementation of the initial Myco481 mutant with the wild type gene confirmed that the phenotype of this mutant was due to loss of LpqW. These studies suggest that LpqW has a role in regulating the flux of early PIM intermediates into polar PIM or LAM biosynthesis. They also suggest that AcPIM4 is the likely branch point intermediate in polar PIM and LAM biosynthesis.},
	keywords = {Cell Membrane, Gene Expression Regulation, Bacterial, Genes, Bacterial, Lipopolysaccharides, Mutation, Mycobacterium smegmatis, Phenotype, Phosphatidylinositols, Virulence},
	issn = {0021-9258},
	doi = {10.1074/jbc.M511709200},
	author = {Kovacevic, Svetozar and Anderson, Dianne and Morita, Yasu S and Patterson, John and Haites, Ruth and McMillan, Benjamin N I and Coppel, Ross and McConville, Malcolm J and Billman-Jacobe, Helen}
}
