title: Spontaneous and ICR191-A-induced frameshift mutations in the A gene of Escherichia coli tryptophan synthetase.
abstract: Frameshift mutant trpA21 was isolated after ultraviolet treatment and frameshift mutant trpA540 after ICR191-A (an acridine derivative) treatment of wild-type Escherichia coli K-12. The A proteins of spontaneous and ICR191-A-induced partial revertants of these mutants contained altered amino acid sequences one residue shorter than the comparable sequence in the A protein of wild-type bacteria. The data support the conclusion that ICR191-A causes frameshift mutations. The findings further indicate that both base additions and deletions are elicited by ICR191-A treatment and that mutagenesis by this compound sometimes affects more than one base pair. ICR191-A also weakly reverts some missense mutants. Analyses of the relevant peptides of the purified A protein show single amino acid replacements compatible with single base-pair changes. In addition, we found that some spontaneously revertible ICR191-A- and ultraviolet light-induced frameshift mutants are not further stimulated to revert by exposure to ultraviolet light.
mesh_terms: D000166:Acridines / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001426:Bacterial Proteins / Q000032:analysis; D004926:Escherichia coli; D005796:Genes; D005815:Genetic Code; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D014364:Tryptophan / Q000096:biosynthesis
chemical_list: D000166:Acridines; D000596:Amino Acids; D001426:Bacterial Proteins; D009153:Mutagens; D014364:Tryptophan