Nucleotide sequence of a Bacillus subtilis arginine regulatory gene and homology of its product to the Escherichia coli arginine repressor

Abstract

In Bacillus subtilis, arginine represses its biosynthetic enzymes and activates its catabolic ones via a regulator gene ahrC. A 6.2-kb Eco RI fragment of B. subtilis chromosomal DNA that includes the ahrC gene has previously been cloned. Gene ahrC was localised in a 0.8-kb Hin dIII sub-fragment whose nucleotide sequence was determined. An open reading frame (ORF) was present whose translated amino acid sequence showed homology to that of the Escherichia coli arginine repressor encoded by that organism's argR gene. That this ORF corresponded to ahrCwas confirmed by (i) the location of the transposen m an ahrC::Tn917 insertion mutant within the ORF; and (ii) by the appearance of an AhrC - phenotype when plasmids carrying restriction fragments lying wholly within this ORF were permitted to integrate by Campbell-type recombination into the B. subtilis chromosome. This represents the first description of a repressor in a ‘housekeeping’ biosynthetic system in a Bacillus, and indeed of homology between regulatory proteins for any ‘housekeeping’ system across such a wide taxonomie barrier among prokaryotes.