Structure and properties of a hybrid tryptophan synthetase of alpha chain produced by genetic exchange between Escherichia coli and Salmonella typhimurium.

Genetic exchange between the structural genes for the alpha chain of tryptophan synthetase [tryptophan synthase; L-serine hydro-lyase (adding indoleglycerol-phosphate), EC 4.2.1.20] of E. coli and S. typhimurium yielded recombinant genes that specified functional hybrid polypeptides. The alpha chains produced by three recombinants appeared to be identical but differed from those of E. coli and S. typhimurium by at least 27 and 8 amino acid residues, respectively. In vivo and in vitro tests of enzyme function suggest that the hybrid alpha chains are near-equivalent to their fully active parental proteins.