Chromosomal location of the Bacillus subtilis aspartokinase II gene and nucleotide sequence of the adjacent genes homologous to uvrC and trx of Escherichia coli

The aspartokinase II (ask) operon of Bacillus subtilis consists of two in-phase overlapping genes that encode the two subunits of the lysine-sensitive isoenzyme of aspartokinase (ATP:L-aspartate 4-phosphotransferase, EC 2.7.2.4). Transduction mapping of the ask operon, inactivated by recombinational insertion of a cat marker, indicates a chromosomal location (about 253 degrees) between leuA and aroG. ask is thus remote from aecB, eliminating aecB as a possible locus for the structural gene of aspartokinase II, but close to aecA and uvrB. The nucleotide sequence of a 2 kb DNA fragment just upstream of the ask operon was determined and found to contain two open reading frames. The deduced amino acid sequence of the distal reading frame exhibits extensive homology with Escherichia coli thioredoxin and that of the proximal one, which overlaps with the ask promoter, is homologous to the deduced product of the E. coli uvrC gene. Insertional mutagenesis of the proximal open reading frame led to a mitomycin-sensitive phenotype, consistent with a role in DNA repair. In conjunction with the data of M. Petricek, L. Rutberg & L. Hederstedt [FEMS Microbiology Letters 61, 85-88] our results define the nucleotide sequence of an 8.8 kb segment of the B. subtilis chromosome near 253 degrees and the following order of genes: trx-uvrB-ask-orfX-sdhC-sdhA-sdhB-orfY++ +-gerE.