Cloning and characterization of the glutamate dehydrogenase gene in Bacillus licheniformis

The gdhA genes of IRC-3 GDH-strain and IRC-8 GDH(+) strain were cloned, and they both successfully complemented the nutritional lesion of an E. coli g lutamate auxotroph, Q100 GDH(-). However, the gdhA gene from the mutant IRC -8 GDH(+) strain failed to complement the glutamate deficiency of the wild type strain IRC-3. The gdhA genes of the wild type and mutant origin were s equenced separately. No nucleotide difference was detected between them. Fu rther investigations indicated that the gdhA genes were actively expressed in both the wild type and the mutant. Additionally, no GDH inhibitor was fo und 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-translation al level of the gdhA expression. Examination of the deduced amino acid sequ ence of Bacillus licheniformis GDH revealed the presence of the motifs char acteristic of the family I -type hexameric protein, while the GDH of Bacill us subtilis belongs to family II.