We report the overexpression, purification, and properties of the regulatory protein, G1nR, for glutamine synthetase synthesis of Bacillus cereus. The protein was found to be a dimer with a molecular weight of approximately 30, 000, and its subunit molecular weight was 15, 000 in agreement with that (15, 025) of deduced amino acid sequence of G1nR. The purified G1nR protein bound specifically to the promoter region of the glnRA operon of B. cereus and Bacillus subtilis. The binding of the G1nR protein to the DNA fragment was enhanced by the presence of glutamine synthetase, the product of glnA, of B. cereus or B. subtilis, although the affinity of the G1nR protein for DNA was not affected in the presence of glutamate, glutamine, Mg2+, Mn2+, or ammonia. These results indicate the existence of an interaction between G1nR and glutamine synthetase, and support the hypothesis that the regulation of glnA expression requires both G1nR protein and glutamine synthetase in Bacillus.
The Japanese Biochemical Society