title: Compartmentalization of lipid biosynthesis in mycobacteria.
abstract: The plasma membrane of Mycobacterium sp. is the site of synthesis of several distinct classes of lipids that are either retained in the membrane or exported to the overlying cell envelope. Here, we provide evidence that enzymes involved in the biosynthesis of two major lipid classes, the phosphatidylinositol mannosides (PIMs) and aminophospholipids, are compartmentalized within the plasma membrane. Enzymes involved in the synthesis of early PIM intermediates were localized to a membrane subdomain termed PMf, that was clearly resolved from the cell wall by isopyknic density centrifugation and amplified in rapidly dividing Mycobacterium smegmatis. In contrast, the major pool of apolar PIMs and enzymes involved in polar PIM biosynthesis were localized to a denser fraction that contained both plasma membrane and cell wall markers (PM-CW). Based on the resistance of the PIMs to solvent extraction in live but not lysed cells, we propose that polar PIM biosynthesis occurs in the plasma membrane rather than the cell wall component of the PM-CW. Enzymes involved in phosphatidylethanolamine biosynthesis also displayed a highly polarized distribution between the PMf and PM-CW fractions. The PMf was greatly reduced in non-dividing cells, concomitant with a reduction in the synthesis and steady-state levels of PIMs and amino-phospholipids and the redistribution of PMf marker enzymes to non-PM-CW fractions. The formation of the PMf and recruitment of enzymes to this domain may thus play a role in regulating growth-specific changes in the biosynthesis of membrane and cell wall lipids.
authors.affiliation: Department of Biochemistry and Molecular Biology, The B1021 Molecular Sciences and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Yasu S
authors.initials: YS
authors.lastname: Morita
authors.forename: René
authors.initials: R
authors.lastname: Velasquez
authors.forename: Ellen
authors.initials: E
authors.lastname: Taig
authors.forename: Ross F
authors.initials: RF
authors.lastname: Waller
authors.forename: John H
authors.initials: JH
authors.lastname: Patterson
authors.forename: Dedreia
authors.initials: D
authors.lastname: Tull
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Williams
authors.forename: Helen
authors.initials: H
authors.lastname: Billman-Jacobe
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: McConville
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D001671:Biochemistry / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D006388:Hemagglutinins / Q000737:chemistry; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008362:Mannosides / Q000737:chemistry*; D008364:Mannosyltransferases / Q000737:chemistry; D008854:Microscopy, Electron; D008954:Models, Biological; D020102:Mycobacterium smegmatis / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010716:Phosphatidylinositols / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D017434:Protein Structure, Tertiary; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D006388:Hemagglutinins; D008055:Lipids; D008362:Mannosides; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D010743:Phospholipids; C483858:phosphatidylethanolamine; D008364:Mannosyltransferases; C400532:PimB protein, Mycobacterium tuberculosis