Molecular cloning of the leub genes from Mycobacterium bovis BCG and Mycobacterium tuberculosis

A gene responsible for the biosynthesis of leucine has been cloned by the complementation of the Escherichia coli leuB6 auxotroph mutant after transformation with the Mycobacterium bovis BCG genomic DNA library, which was constructed by ligating the partially digested BCG DNA with Sau3AI into the pUC 19 digested with BamHI. Sequencing of the leuB gene of BCG revealed an ORF (open reading frame) of 1,011 bp encoding isopropytmalate dehydrogenase with a calculated molecular weight of 42 kDa. The leuB gene of Mycobacterium tuberculosis isolated from Korean tuberculosis patient is shown to be identical to that of BCG except one bp.