AN ALTERATION IN THE PRIMARY STRUCTURE OF A PROTEIN PREDICTED ON THE BASIS OF GENETIC RECOMBINATION DATA

Abstract

The A protein of the tryptophan synthetase of mutant A-46 of E. coli K-12 was found to differ from the normal A protein by a single amino acid substitution, glutamic acid for glycine. The substitution results in alterations of several of the properties of the A protein. The glycine residue replaced by glutamic acid in the A-46 protein is the same glycine replaced by arginine in the A protein of the closely linked mutant, A-23. The recombination observed between the two strains probably represents recombinational events between different nucleo-tides in the same coding unit. Mutant A-95 and three other A mutants that map at the A-46 site form altered A proteins that exhibit the same properties as the A-46 protein. The A-95 protein was found to have the same amino acid substitution at the same position as the A-46 protein.