Structural interactions between amino acid residues at positions 22 and 211 in the tryptophan synthetase alpha chain of Escherichia coli.

Construction and characterization of double mutants altered in the structural gene of the tryptophan synthetase alpha chain of Escherichia coli revealed interactions between amino acid residues at positions 22 and 211. These interactions are specific for the particular amino acid residue at position 211. The results indicate also that amino acid residues which appear to be functionally near-equivalent in one configuration may strongly influence the activity of a protein with a subsequent change at another site. Seven independent suppressors of trpA218 (Leu22-Ser211) were isolated. Their properties suggest that all seven may suppress the codon (AGU/C) for Ser211. Six of the seven are co-transducible with glyV, the structural gene for the GGU/C-specific tRNA(Gly).