Nucleotide sequence of the genes for tryptophan synthase in Pseudomonas aeruginosa

We have determined the DNA sequence of the two adjacent genes for the alphaand beta chains of tryptophan synthase in Pseudomonas aeruginosa, alongwith 34 5'-flanking and 799 3'-flanking base pairs. The gene order is trpBAas predicted from earlier genetic studies, and the two cistrons overlap by4 bp; a ribosome binding site for the second gene is evident in the codingsequence of the first gene. We have also determined the location of threelarge deletions eliminating portions of each gene. A detailed comparison ofthe deduced P. aeruginosa amino acid sequence with those published for E.coli, Bacillus subtilis, and Saccharomyces cerevisiae shows much similaritythroughout the beta and most of the alpha subunit. Most of the residuesimplicated by chemical modification or mutation as being critical forenzymatic activity are conserved, along with many others, suggesting thatthree-dimensional structure has remained largely constant during evolution.We also report the construction of a recombinant plasmid that overproducesa slightly modified alpha subunit from P. aeruginosa that can form afunctionally effective multimer with normal E. coli beta 2 subunit in vivo.