Mutagenesis of amino acid residues required for binding of corepressors to the purine repressor.
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.
Choi
K Y
KY
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153.
Lu
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Zalkin
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D000596:Amino Acids / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D004274:DNA, Recombinant; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009875:Operator Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D000596:Amino Acids; D001426:Bacterial Proteins; D004274:DNA, Recombinant; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C065825:PurR protein, Bacteria; C489317:PurR protein, E coli; D012097:Repressor Proteins