CLONING AND SEQUENCING OF THE ILVBNC GENE-CLUSTER FROM MYCOBACTERIUM-AVIUM

Disseminated Mycobacterium avium (Ma)-M. intracellulare disease is a p revalent opportunistic infection in patients with Acquired Immune Defi ciency Syndrome. Mycobacteria produce a variety of fatty acids which p rovide the first line of defence against potentially lethal environmen tal conditions. The metabolism of the branched-chain amino acids (BCAA ) could be correlated to the production of branched-chain fatty acids in mycobacteria. In order to develop a better understanding of Mycobac terium BCAA biosynthesis, three genes, ilvBN and ilvC, encoding acetoh ydroxy acid synthase (AHS) and acetohydroxy acid isomeroreductase (IR) , respectively, were cloned from Ma. The genes were isolated by screen ing a Ma genomic library with a heterologous probe. The deduced amino acid sequences revealed significant homology to the AHS and IR protein s from other bacterial species.