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J. Bacteriol. doi:10.1128/JB.01370-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification and characterization of two novel methyltransferase genes that determine the serotype 12-specific structure on glycopeptidolipids of Mycobacterium intracellulare

Department of Microbiology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan, Department of Host Defense, Osaka City University Graduate School of Medicine, Osaka, Japan, Japan BCG Laboratory, Tokyo, Japan, Department of Immunology, National Institute of Infectious Diseases, Tokyo, Japan, Molecular Epidemiology Division, Mycobacterium Reference Center, The Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Tokyo, Japan

^* To whom correspondence should be addressed. Email: n-nakata{at}nih.go.jp.

	Abstract

The Mycobacterium avium complex is distributed ubiquitously in the environment. It is an important cause of pulmonary and extrapulmonary diseases in humans and animals. These species produce polar glycopeptidolipids (GPLs); of particular interest is their serotype-specific antigenicity. Several reports have described that GPL structure may play an important role in bacterial physiology, pathogenesis, and host immune response. Recently, we determined the complete structure of GPL derived from Mycobacterium intracellulare serotype 7 and characterized the serotype 7 GPL-specific gene cluster. The structure of serotype 7 GPL was closely resembled that of serotype 12 GPL, except for O-methylation. In the present study, we isolated and characterized the serotype 12-specific gene cluster involved in glycosylation of the GPL. Ten open reading frames (ORFs) and one pseudogene were observed in the cluster. Genetic organization of the serotype 12-specific gene cluster resembled that of serotype 7, but two novel ORFs (orfA and orfB) encoding putative methyltransferases were present in the cluster. Functional analyses revealed that the orfA and orfB respectively encode methyltransferases that synthesize O-methyl groups at the C4 position in the rhamnose residue next to the terminal hexose and at the C3 position in the terminal hexose. Our results show that these two methyltransferase genes determine the structural difference of serotype 12-specific GPL from serotype 7-specific GPL.