title: Translational restarts: AUG reinitiation of a lac repressor fragment.
abstract: An early, spontaneous amber mutation in the lac i-gene allows translational reinitiation, which results in a mutant lac repressor. Comparison of the amino-terminal sequence of this mutant repressor with the partial amino-acid sequence of the wild-type lac repressor shows that reinitiation occurs at the first internal AUG codon, and results in a mutant protein lacking 42 residues at the amino-terminal end. This protein binds the inducer isopropyl-beta-D-thiogalactoside with normal affinity, and is capable of maintaining a tetrameric structure; however, it does not repress in vivo. These data suggest that the amino-terminal portion of the wild-type lac repressor is necessary either for direct binding to the lac operator or for the correct conformation for binding to DNA.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology; D000595:Amino Acid Sequence; D000936:Antigen-Antibody Complex; D001426:Bacterial Proteins / Q000096:biosynthesis*; D001665:Binding Sites; D004586:Electrophoresis; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D005815:Genetic Code; D006150:Guanine Nucleotides / Q000494:pharmacology; D007785:Lactose / Q000096:biosynthesis; D009154:Mutation; D009690:Nucleic Acid Conformation; D010452:Peptide Biosynthesis; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects; D010443:Peptide Chain Termination, Translational / Q000187:drug effects; D011119:Polynucleotides / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D013489:Suppression, Genetic; D014500:Uracil Nucleotides / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D000936:Antigen-Antibody Complex; D001426:Bacterial Proteins; D006150:Guanine Nucleotides; D011119:Polynucleotides; D014500:Uracil Nucleotides; D007785:Lactose