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J. Biol. Chem., Vol. 282, Issue 6, 3531-3538, February 9, 2007

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Substrate Specificity of RdgB Protein, a Deoxyribonucleoside Triphosphate Pyrophosphohydrolase^*

From the Department of Biological Sciences, University at Albany, State University of New York, Albany, New York 12222

We have previously reported the identification of a DNA repair system in Escherichia coli for the prevention of the stable incorporation of noncanonical purine dNTPs into DNA. We hypothesized that the RdgB protein is active on 2'-deoxy-N-6-hydroxylaminopurine triphosphate (dHAPTP) as well as deoxyinosine triphosphate. Here we show that RdgB protein and RdgB homologs from Saccharomyces cerevisiae, mouse, and human all possess deoxyribonucleoside triphosphate pyrophosphohydrolase activity and that all four RdgB homologs have high specificity for dHAPTP and deoxyinosine triphosphate compared with the four canonical dNTPs and several other noncanonical (d)NTPs. Kinetic analysis reveals that the major source of the substrate specificity lies in changes in K_m for the various substrates. The expression of these enzymes in E. coli complements defects that are caused by the incorporation of HAP and an endogenous noncanonical purine into DNA. Our data support a preemptive role for the RdgB homologs in excluding endogenous and exogenous modified purine dNTPs from incorporation into DNA.

Received for publication, September 8, 2006 , and in revised form, October 25, 2006.

^* This work was supported by National Science Foundation Grant MCB-0115188 (to R. P. C.) and National Institutes of Health Grant NCRR 1 C06 RR015464. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Dept. of Biological Sciences, The University at Albany, SUNY, 1400 Washington Ave., Albany, NY 12222. Tel.: 518-442-4331; Fax: 518-442-4767; E-mail: moose{at}albany.edu.

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