Tryptophan Synthetase α Chain Positions Affected by Mutations near the Ends of the Genetic Map of trpA of Escherichia coli

The codons specifying the amino acid residues at positions 15 and 243 in the α chain of Escherichia coli tryptophan synthetase are altered in nonsense mutants whose mutations lie at the ends of the genetic map of trpA, the structural gene of the α chain. A missense mutant, trpA218, altered near the beginning of trpA, has an amino acid change at position 22 in the α chain. The relationship of the genetic map of trpA to the amino acid sequence of the α chain is considered.