Structure of the specific oligosaccharides from the glycopeptidolipid antigens of serovars in the Mycobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum complex

Abstract

The specific oligosaccharide units of the C-mycosidic glycopeptidolipid antigens from serovarieties in the Myobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum complex were liberated as oligosaccharide alditols by treatment of the glycopeptidolipids with alkaline borohydride. The complete structures of the oligosaccharide alditols have been derived from their 1H-NMR spectra or those of their permethylated (or pertrideuteriomethylated) derivatives, the mass spectra of the methylated derivatives, and from methylation fragmentation analysis. Periodate oxidation was also used to confirm the position of the link between the ultimate and penultimate sugars. The following structures are proposed (with some extrapolation of enantiomeric configurations where evidence for assignment is not yet complete) for the oligosaccharide alditols: Serovar 9 2,3-Me2-alpha-L-Fucp-(1 leads to 4)-2,3-Me2-alpha-L-Fucp-(1 leads to 3)-alpha-L-Rhap-(1 leads to 2)-6-deoxy-L-Talol Serovar 25 2-Me-alpha-L-Fucp-(1 leads to 4)-2-Me-alpha-L-Fucp-(1 leads to 3)-alpha-L-Rhap-(1 leads to 2)-6-deoxy-L-talol Serovar 8 4,6-(1'-carboxyethylidene)-3-Me-beta-D-Glcp-(1 leads to 3)-alpha-L-Rhap-(1 leads to 2)-6-deoxy-L-Talol Thus, 6-deoxytalitol (6-deoxytalose in the original glycopeptidolipid) invariably occupies the reducing terminus. Rhamnose is invariably the penultimate sugar, and the link between rhamnose and 6-deoxytalose is invariably alpha 1 leads to 2. Moreover, the results point to the outer one or two appendages for the provision of individually distinctive features required for antigen specificity. The abbreviations used are: serovar, serologically distinct varieties; Me, methyl; Fucp, fucopyranose; Rhap, rhamnopyranose; Talol, talitol.