ALTERED TRANSCRIPTION ACTIVATION SPECIFICITY OF A MUTANT FORM OF BACILLUS-SUBTILIS GLTR, A LYSR FAMILY MEMBER

A mutation (gltR24) that allows Bacillus subtilis glutamate synthase ( gltAB) gene expression in the absence of its positive regulator, GltC, was identified, Cloning and sequencing of the gltR gene revealed that the putative gltR product belongs to the LysR family of transcription al regulators and is thus related to GltC, A null mutation in gltR had no effect on gltAB expression under any environmental condition teste d, suggesting that gltR24 is a gain-of-function mutation, GltR24-depen dent transcription of gltAB, initiated at the same base pair as GltC-d ependent transcription, was responsive to the nitrogen source in the m edium and required the integrity of sequences upstream of the gltAB pr omoter that are also necessary for GltC-dependent expression, Expressi on of the gltC gene, transcribed divergently from gltA from an overlap ping promoter, was not affected by GltR, Both wild-type GltR and GltR2 4 negatively regulated their own expression, The gltR gene was mapped to 233 degrees on the B. subtilis chromosome, very close to the azlB l ocus.