Cloning and Sequencing of Bacillus stearothermophilus Tryptophan Synthase Genes

The tryptophan synthase genes, trpA and trpB, of Bacillus stearothermophilus IFO13737 were cloned by transformation of tryptophan auxotrophic mutations of the trp genes into Escherichia coli. The genes are located in the order of trpB and trp A, according to their coding orientation, in a 2.5 kb EcoRy-Hindlll DNA fragment. The complete nucleotide sequence of this DNA was determined. The trp A and trpB genes consist of 810bp (269 amino acid residues) and 1215bp (404 amino acid residues), respectively. The 5′-proximal portion of the trpB gene was found to overlap 20 nucleotides of the upstream coding region of the trpA gene. The homology of the amino acid sequences of the trp gene products of trp A and trpB of B. stearothermophilus is 35 and 50 %, respectively, to those of E. coli, and 55 and 70 %, respectively, to those of B. subtilis.