Translational Restarts: AUG Reinitiation of a lac Repressor Fragment

AUTOR(ES)

Platt, Terry

RESUMO

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-β-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.

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