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J. Biol. Chem., Vol. 269, Issue 39, 24066-24072, 09, 1994

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

KY Choi, F Lu and H Zalkin
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153.

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.
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This article has been cited by other articles:

				H. Xu, M. Moraitis, R. J. Reedstrom, and K. S. Matthews Kinetic and Thermodynamic Studies of Purine Repressor Binding to Corepressor and Operator DNA J. Biol. Chem., April 10, 1998; 273(15): 8958 - 8964. [Abstract] [Full Text] [PDF]

				M. Schumacher, K. Choi, H Zalkin, and R. Brennan Crystal structure of LacI member, PurR, bound to DNA: minor groove binding by alpha helices Science, November 4, 1994; 266(5186): 763 - 770. [Abstract] [PDF]