Initiation of methylglucose lipopolysaccharide biosynthesis in mycobacteria.
BACKGROUND
Mycobacteria produce two unique families of cytoplasmic polymethylated polysaccharides -- the methylglucose lipopolysaccharides (MGLPs) and the methylmannose polysaccharides (MMPs) -- the physiological functions of which are still poorly defined. Towards defining the roles of these polysaccharides in mycobacterial physiology, we generated knock-out mutations of genes in their putative biosynthetic pathways.


RESULTS
We report here on the characterization of the Rv1208 protein of Mycobacterium tuberculosis and its ortholog in Mycobacterium smegmatis (MSMEG_5084) as the enzymes responsible for the transfer of the first glucose residue of MGLPs. Disruption of MSMEG_5084 in M. smegmatis resulted in a dramatic decrease in MGLP synthesis directly attributable to the almost complete abolition of glucosyl-3-phosphoglycerate synthase activity in this strain. Synthesis of MGLPs in the mutant was restored upon complementation with wild-type copies of the Rv1208 gene from M. tuberculosis or MSMEG_5084 from M. smegmatis.


CONCLUSIONS
This is the first evidence linking Rv1208 to MGLP biosynthesis. Thus, the first step in the initiation of MGLP biosynthesis in mycobacteria has been defined, and subsequent steps can be inferred.
Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA.
Devinder
D
Kaur
Ha
H
Pham
Gérald
G
Larrouy-Maumus
Michel
M
Rivière
Varalakshmi
V
Vissa
Marcelo E
ME
Guerin
Germain
G
Puzo
Patrick J
PJ
Brennan
Mary
M
Jackson
D001426:Bacterial Proteins / Q000502:physiology*; D002855:Chromatography, Thin Layer; D005816:Genetic Complementation Test; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000032:analysis / Q000096:biosynthesis*; D021241:Spectrometry, Mass, Electrospray Ionization
D001426:Bacterial Proteins; C057520:O-methylglucose polysaccharide; D011135:Polysaccharides, Bacterial; D005964:Glucosyltransferases; C534794:glucosyl-3-phosphoglycerate synthase, Mycobacterium tuberculosis