title: The lipoprotein LpqW is essential for the mannosylation of periplasmic glycolipids in Corynebacteria.
abstract: Phosphatidylinositol mannosides (PIM), lipomannan (LM), and lipoarabinomannan (LAM) are essential components of the cell wall and plasma membrane of mycobacteria, including the human pathogen Mycobacterium tuberculosis, as well as the related Corynebacterineae. We have previously shown that the lipoprotein, LpqW, regulates PIM and LM/LAM biosynthesis in mycobacteria. Here, we provide direct evidence that LpqW regulates the activity of key mannosyltransferases in the periplasmic leaflet of the cell membrane. Inactivation of the Corynebacterium glutamicum lpqW ortholog, NCgl1054, resulted in a slow growth phenotype and a global defect in lipoglycan biosynthesis. The NCgl1054 mutant lacked LAMs and was defective in the elongation of the major PIM species, AcPIM2, as well as a second glycolipid, termed Gl-X (mannose-α1-4-glucuronic acid-α1-diacylglycerol), which function as membrane anchors for LM-A and LM-B, respectively. Elongation of AcPIM2 and Gl-X was found to be dependent on expression of polyprenol phosphomannose (ppMan) synthase. However, the ΔNCgl1054 mutant synthesized normal levels of ppMan, indicating that LpqW is not required for synthesis of this donor. A spontaneous suppressor strain was isolated in which lipoglycan synthesis in the ΔNCgl1054 mutant was partially restored. Genome-wide sequencing indicated that a single amino acid substitution within the ppMan-dependent mannosyltransferase MptB could bypass the need for LpqW. Further evidence of an interaction is provided by the observation that MptB activity in cell-free extracts was significantly reduced in the absence of LpqW. Collectively, our results suggest that LpqW may directly activate MptB, highlighting the role of lipoproteins in regulating key cell wall biosynthetic pathways in these bacteria.
authors.affiliation: Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Victoria 3800, Australia.
authors.forename: Arek K
authors.initials: AK
authors.lastname: Rainczuk
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamaryo-Botte
authors.forename: Rajini
authors.initials: R
authors.lastname: Brammananth
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Stinear
authors.forename: Torsten
authors.initials: T
authors.lastname: Seemann
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: McConville
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crellin
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways; D002473:Cell Wall / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D020868:Gene Silencing; D018390:Gene Targeting; D005816:Genetic Complementation Test; D006017:Glycolipids / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism*; D008364:Mannosyltransferases / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D019897:Periplasm / Q000378:metabolism*; D013489:Suppression, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006017:Glycolipids; D008070:Lipopolysaccharides; D008074:Lipoproteins; C064351:lipomannan; D008364:Mannosyltransferases; D008358:Mannose