EXPRESSION OF THE CORE LIPOPEPTIDE OF THE GLYCOPEPTIDOLIPID SURFACE-ANTIGENS IN ROUGH MUTANTS OF MYCOBACTERIUM-AVIUM

Toward studying the genetics, biosynthesis, and roles in the pathogene sis of the dominant surface glycopeptidolipid antigens of Mycobacteriu m avium, rough colony variants of M. avium serovar 2 were picked, cult ured in quantity, and their lipid composition examined. Two of the rou gh (Rg) variants, Rg-3 and Rg-4, were devoid of glycopeptidolipids or any more elemental structures and thus were similar to those described previously. Two others, Rg-0 and Rg-1, each contained two novel lipop eptides, devoid of any of the carbohydrate substituents that confer se rotypic activity on the glycopeptidolipids. The application of gas chr omatography, fast atom bombardment-mass spectrometry and H-1 NMR to li popeptide I established the structure C32:2-beta-OH-fatty acyl-D-Phe-D -allo-Thr-D-Ala-L-alaninol. Lipopeptide II represented a minor variati on of this structure: C32:1-beta-OH-fatty acyl-D-Phe-D-allo-Thr-D-Ala- L-alaninol. These newly discovered lipopeptides are identical to the f atty acyl-tripeptide-amino alcohol ''core'' component of the glycopept idolipids of the M. avium complex, and thus the Rg-0 and Rg-1 variants represent a form of ''deep rough'' mutation in M. avium. Separately, we report that these rough variants of M. avium differ genetically fro m the smooth, virulent form by major deletions of portions of the gene s responsible for glycopeptidolipid synthesis (Belisle, J. T., Klaczki ewicz, K., Brennan, P. J., Jacobs, W. R., Jr., and Inamine, J. M. (199 3) J. Biol. Chem. 268, 10517-10523). The isolation of different sets o f spontaneous mutants of M. avium differentially defective in the capa city to synthesize glycopeptidolipids provides the means to explore th eir biosynthesis and roles in opportunistic pathogenesis.