Cloning of genes for proline and leucine biosynthesis from Brucella abortus by functional complementation in Escherichia coli.

By selecting for growth of Escherichia coli mutant strains in the absence of the required amino acid, clones were found in a Brucella abortus library carrying genes for glutamyl phosphate reductase (proA) and beta-isopropylmalate dehydrogenase (leuB). These clones hybridized to unique fragments in a genomic digest of B. abortus DNA. The proA-complementing DNA was found in a region of 1.3 kb, which directed the synthesis of a protein of 48,000 Da with a pI of 6.3 in maxicells. The leuB-complementing activity was in a region of 1.4 kb and directed synthesis of a protein of 46,000 Da with a pI of 5.9.