A GMC oxidoreductase homologue is required for acetylation of glycopeptidolipid in Mycobacterium smegmatis

Abstract

The Mycobacterium tuberculosis Rv3409c gene is required for modulation of the Toll-like receptor 2 (TLR-2) signaling response in infected macrophages. Although each is annotated as encoding a cholesterol oxidase, neither Rv3409c nor its ortholog MSMEG1604 is required for the metabolism of cholesterol in mycobacteria. Here we report that a unique lipid, L1334, accumulates in a MSMEG1604 transposon mutant in the Mycobacterium smegmatis cell envelope. L1334 is a polar glycopeptidolipid that is hyperrhamnosylated and in which the 6-deoxytalose moiety is not acetylated. The alteration of L1334 acetylation is consistent with a reduced level of interference with TLR-2 signaling in mutant infected macrophages.

Figure 1

Enlarged region of the MALDI-TOF mass spectra of total lipids of M. smegmatis mc2155, the Myc11:pMS100 complement, the Myc11:pMS101 complement, and Myc11. The full spectra are shown in Figure S1 of the Supporting Information.

Figure 2

(A) Proposed structure of L1334. Arrows denote fragments lost in MSⁿ experiments shown in Figure S3 of the Supporting Information. Regions of ¹H nuclear magnetic resonance spectra corresponding to (B) four methyl ether and (C) three sugar anomeric hydrogen resonances.