Abstract：
:Site-directed mutagenesis was used to construct mutant Trp repressors with each of the 38 possible single amino acid changes of the first 2 amino acid residues (Ile79 and Ala80) in the second "recognition" alpha-helix of the helix-turn-helix DNA-binding motif. Eight of these mutant repressors with Ile79 and Ala80 changes are more active than the wild-type protein when tryptophan is limiting, and are super-aporepressors. Eleven mutant repressors have extended DNA-binding specificies in vivo, and bind operators which the wild-type repressor cannot. One mutant repressor, Lys79, has a classical altered specificity phenotype in vivo, and binds the wild-type trp operator less well than wild-type repressor, yet binds a mutant operator better than wild-type repressor. A site-specific nuclease was derived from Lys79 repressor by constructing a double-mutant protein with Lys79 and a sole cysteine residue, Cys49, and alkylating this cysteine with a 1,10-phenanthroline-copper adduct. This nuclease has an altered specificity of DNA binding in vitro. When activated by the addition of thiol and hydrogen peroxide, the Lys79 nuclease cleaves operator DNA within its new recognition sequence with high efficiency.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Pfau J,Arvidson DN,Youderian P,Pearson LL,Sigman DSdoi
10.1021/bi00203a038subject
Has Abstractpub_date
1994-09-20 00:00:00pages
11391-403issue
37eissn
0006-2960issn
1520-4995journal_volume
33pub_type
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