Cloning and Characterization of theBacillus subtilis birAGene Encoding a Repressor of the Biotin Operon

TheBacillus subtilis birAgene, which regulates biotin biosynthesis, has been cloned and characterized. The birAgene maps at 202&on theB. subtilischromosome and encodes a 36,200-Da protein that is 27% identical to Escherichia coli BirA protein. Three independent mutations in birA that lead to deregulation of biotin synthesis alter single amino acids in the amino-terminal end of the protein. The amino-terminal region that is affected by these threebirAmutations shows sequence similarity to the helix-turn-helix DNA binding motif previouslyidentifiedinE.coliBirAprotein.B.subtilisBirAproteinalsopossessesbiotin-proteinligaseactivity, as judged by its ability to complement a conditional lethalbirAmutant ofE. coli.