Characterization of the spoivb and recn loci of bacillus-subtilis

Academic Article
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publication date

  • March 1990

abstract

  • Two independent genes, recN and spoIVB, along with their respective promoter and termination regions, were discovered and sequenced in the 3.4-kilobase region between the ahrC and spoOA genes at map position 216 in the Bacillus subtilis chromosome map. The gene encoding a 576-amino-acid protein, which maintains a high homology with the Escherichia coli recN gene product, was adjacent to ahrC. The sequence revealed a 64,472-dalton polypeptide which contained a conserved ATP-binding site and possible lexA-type regulatory binding sequences in its promoter region. A second open reading frame identified as the spoIVB gene was directly downstream of recN. It consisted of 1,275 nucleotides which coded for a 425-amino-acid polypeptide with a molecular weight of 45,976. Phenotypic, genetic, and transcriptional analyses confirmed that this gene was spoIVB. Although no chloroform-resistant spores were produced by spoIVB-inactivated strains, under microscopic examination, phase-gray forespores were visible. The spoIVB165 mutation was localized to a 200-base-pair region in the amino-terminal portion of the polypeptide, spoIVB was not transcribed until hour 2 of sporulation in wild-type B. subtilis cells, as determined by beta-galactosidase activity assays from lacZ transcriptional fusion constructions. We found no amino acid sequence homology between the spoIVB gene product and other known bacterial proteins.