title: Ppm1-encoded polyprenyl monophosphomannose synthase activity is essential for lipoglycan synthesis and survival in mycobacteria.
abstract: The biosynthesis of mycobacterial mannose-containing lipoglycans, such as lipomannan (LM) and the immunomodulator lipoarabinomanan (LAM), is carried out by the GT-C superfamily of glycosyltransferases that require polyprenylphosphate-based mannose (PPM) as a sugar donor. The essentiality of lipoglycan synthesis for growth makes the glycosyltransferase that synthesizes PPM, a potential drug target in Mycobacterium tuberculosis, the causative agent of tuberculosis. In M. tuberculosis, PPM has been shown to be synthesized by Ppm1 in enzymatic assays. However, genetic evidence for its essentiality and in vivo role in LM/LAM and PPM biosynthesis is lacking. In this study, we demonstrate that MSMEG3859, a Mycobacterium smegmatis gene encoding the homologue of the catalytic domain of M. tuberculosis Ppm1, is essential for survival. Depletion of MSMEG3859 in a conditional mutant of M. smegmatis resulted in the loss of higher order phosphatidyl-myo-inositol mannosides (PIMs) and lipomannan. We were also able to demonstrate that two other M. tuberculosis genes encoding glycosyltransferases that either had been shown to possess PPM synthase activity (Rv3779), or were involved in synthesizing similar polyprenol-linked donors (ppgS), were unable to compensate for the loss of MSMEG3859 in the conditional mutant.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.
authors.forename: Amrita K
authors.initials: AK
authors.lastname: Rana
authors.forename: Albel
authors.initials: A
authors.lastname: Singh
authors.forename: Sudagar S
authors.initials: SS
authors.lastname: Gurcha
authors.forename: Liam R
authors.initials: LR
authors.lastname: Cox
authors.forename: Apoorva
authors.initials: A
authors.lastname: Bhatt
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D020043:Genes, Essential; D005816:Genetic Complementation Test; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D008364:Mannosyltransferases / Q000235:genetics* / Q000502:physiology; D050296:Microbial Viability; D020102:Mycobacterium smegmatis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D010641:Phenotype; D017384:Sequence Deletion
chemical_list: D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D008364:Mannosyltransferases; C479135:polyprenyl monophosphomannose synthase, bacteria