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Department of Host Defense, Osaka City University Graduate School of Medicine, Osaka,1 Department of Microbiology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo,2 Molecular Epidemiology Division, Mycobacterium Reference Center, The Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Tokyo,3 Japan BCG Central Laboratory, Tokyo,4 Department of Chemistry, Graduate School of Science, Osaka City University, Osaka, Japan5
Received 18 September 2006/ Accepted 13 November 2006
The nontuberculous Mycobacterium avium-Mycobacterium intracellulare complex (MAC) is distributed ubiquitously in the environment and is an important cause of respiratory and lymphatic disease in humans and animals. These species produce polar glycopeptidolipids (GPLs), and of particular interest is their serotype-specific antigenicity. Structurally, GPLs contain an N-acylated tetrapeptide-amino alcohol core that is glycosylated at the C terminal with 3,4-di-O-methyl rhamnose and at the D-allo-threonine with a 6-deoxy-talose. This serotype nonspecific GPL is found in all MAC species. The serotype-specific GPLs are further glycosylated with a variable haptenic oligosaccharide at 6-deoxy-talose. At present, 31 distinct serotype-specific GPLs have been identified on the basis of oligosaccharide composition, and the complete structures of 14 serotype-specific GPLs have been defined. It is considered that the modification of the GPL structure plays an important role in bacterial physiology, pathogenesis, and host immune responses. In this study, we defined the complete structure of a novel serotype 7 GPL that has a unique terminal amido sugar. The main molecular mass is 1,874, and attached to the tetrapeptide-amino alcohol core is the serotype 7-specific oligosaccharide unit of 4-2'-hydroxypropanoyl-amido-4,6-dideoxy-2-O-methyl-ß-hexose-(1
3)-
-L-rhamnose-(1
3)-
-L-rhamnose-(1
3)-
-L-rhamnose-(1
2)-
-L-6-deoxy-talose. Moreover, we isolated and characterized the serotype 7-specific gene cluster involved in glycosylation of the oligosaccharide. Nine open reading frames (ORFs) were observed in the cluster. Based on the sequence homology, the ORFs are thought to participate in the biosynthesis of the serotype 7 GPL.
Published ahead of print on 22 November 2006.
Supplemental material for this article may be found at http://jb.asm.org/.
Present address: Department of Immunology, National Institute of Infectious Diseases, Tokyo, Japan.
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