Identification of a methyltransferase from Mycobacterium smegmatis involved in glycopeptidolipid synthesis

Abstract

Glycopeptidolipids (GPLs) are major components of the cell walls of several species of mycobacteria. We have isolated a transposon mutant of Mycobacterium smegmatis that is unable to synthesize mature GPLs and that displays a rough colony morphology. The disrupted gene, mtf1, shares a high degree of homology with several S-adenosylmethionine-dependent methyltransferases. The enzyme encoded by mtf1 is required for the methylation of a single rhamnose residue that forms part of the conserved GPL core structure. This conclusion is supported by the finding that (a) the mutant synthesized only GPLs with undermethylated (either mono- or nonmethylated instead of di- or trimethylated) rhamnose resid..