LosA, a Key Glycosyltransferase Involved in the Biosynthesis of a Novel Family of Glycosylated Acyltrehalose Lipooligosaccharides from Mycobacterium marinum

Abstract

Members of the genus 279, 18824 -18833), chromatographically similar glycolipids were assigned to the family of phosphatidylinositol mannosides (PIMs) and a "PimF" (Rv1500) glycosyltransferase implicated in the conversion of a supposed "PIM 5 " to a "PIM 7 . " The present study indicates that these putative PIMs are in fact members of the phosphorus-free LOS family of glycolipids and that the protein product of Rv1500, which we have now termed LosA, is a glycosyltransferase involved in transferring sugars to LOS-III to form LOS-IV of M. marinum.

Unexpected Link between Lipooligosaccharide Biosynthesis and Surface Protein Release in Mycobacterium marinum

“…Lipid Extraction and Analysis-Polar lipids were extracted and analyzed as described in Burguiere et al (16).…”

“…Genes involved in LOS biosynthesis obtained from our screen are depicted in bold and underlined, with the location of individual mutants indicated below the dark gray arrows. LOS biosynthesis defects were shown previously for gene disruption of mm2309, losA, mm2332, mm2333, and papA4 (15,16,18,20) and deletion of region mm2314 to mm2317 (19) (depicted in light gray as a single responsible gene was not assigned). Similar LOS biosynthesis defects are observed in disruption of adjacent genes or genes in close proximity to each other, suggesting genomic clustering.…”

“…Transcriptional regulatory protein Whib-like A9 (1-4)-Glcp-(1-1)-Glcp (16). The addition of xylose together with one or two molecules of the highly unusual sugar caryophyllose (19) produces LOS-II and LOS-III, respectively.…”

“…LOS is a trehalose-based glycolipid present in the mycobacterial outer membrane. This glycolipid has been described for several mycobacterial species, including M. marinum (16) and Mycobacterium canettii of the M. tuberculosis complex (17). Interestingly, other species of the M. tuberculosis complex have lost the ability to produce LOS.…”

Evolution of the Mycobacterial SigK Regulon

“…For instance, comparative analysis has demonstrated conservation of biochemical pathways and a secretory system important for full virulence of M. tuberculosis (7,10). This indicates that genetic elements and the proteins they encode that exist in other mycobacteria either serve an important function in M. tuberculosis pathogenicity or have evolved a specific role in M. tuberculosis complex organisms.…”