Cloning and characterization of the glutamate dehydrogenase gene inBacillus licheniformis

ThegdhA genes of IRC-3 GDH(-)strain and IRC-8 GDH(+) strain were cloned, and they both successfully complemented the nutritional lesion of anE. coli glutamate auxotroph, Q100 GDH(-). However, thegdhA gene from the mutant IRC-8 GDH(+) strain failed to complement the glutamate deficiency of the wild type strain IRC-3. ThegdhA genes of the wild type and mutant origin were sequenced separately. No nucleotide difference was detected between them. Further investigations indicated that thegdhA genes were actively expressed in both the wild type and the mutant. Additionally, no GDH inhibitor was found in the wild type strain IRC-3. It is thus proposed that the inactivity of GDH in wild type is the result of the deficiency at the post-translational level of thegdhA expression. Examination of the deduced amino acid sequence ofBacillus licheniformis GDH revealed the presence of the motifs characteristic of the family I-type hexameric protein, while the GDH ofBacillus subtilis belongs to family II.