Mutagenesis of amino acid residues required for binding of corepressors to the purine repressor

Kang Yell Choi, Fu Lu, Howard Zalkin

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Abstract

The corepressor-binding domain of the Escherichia coli purine repressor (PurR) is homologous with several periplasmic sugar-binding proteins. Four amino acids in PurR were investigated for a role in binding of corepressors. Three of the residues, Asp146, Arg196 and Asp275, are conserved in periplasmic binding proteins for ribose, glucose/galactose, and arabinose and function to bind sugars. A fourth amino acid, Trp147, required for corepressor binding to PurR, corresponds to residues in glucose/galactose, ribose, and arabinose that also have a role in sugar binding. The four mutations that were constructed perturbed the binding of both hypoxanthine and guanine thus providing evidence for a single corepressor site/PurR subunit. The decreased corepressor binding affinity resulted in reduced affinity of mutant repressors for operator DNA in vitro and decreased capacity for repression in vivo. The corepressor-binding site in PurR appears to be similar to the conserved ligand-binding sites in the three periplasmic sugar-binding proteins and in the LacI family of repressors.

Original languageEnglish
Pages (from-to)24066-24072
Number of pages7
JournalJournal of Biological Chemistry
Volume269
Issue number39
Publication statusPublished - 1994 Sep 30

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All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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