Ribonucleotide-diphosphate reductases inactivation

In a study related to the mechanism of inactivation of ribonucleotide diphosphate reductase (RDPR) by 2 -deoxy-2 -substituted nucleotide analogues, it was found that treatment of nucleosides of type 57 (B=Ura, Ade, X=I, Br, Cl, SMe, N3) with tributylstannane and AIBN gave the d4 products 58, whilst with X=F, OMs or OTs, the 3 -deoxysystem 59 was the product. The results pointed to the loss of radicals rather than anions from C-2 during mechanism-based inactivation of RDPR, and the authors suggest some modifications to Stubbe s mechanistic proposals. ... 

EPR investigations of the inactivation of E. coU ribonucleotide reductase with 2 -azido-2 -deoxyuridine 5 -diphosphate Evidence... 

Since 1976 a number of 2 -substituted 2 -deoxynucleoside 5 -diphosphates have been shown to be mechanism-based inactivators of the ribonucleotide reductases from a variety of sources (Table I). This work was extended by Stubbe and Kozarich 50, 51), who studied the reaction of several 2 -halo-substituted 2 -deoxynucleoside 5 -diphosphates with RDPR. Incubation of RDPR with CIUDP, 2 -deoxy-2 -fluoroadenosine 5 -diphosphate (FADP), or 2 -deoxy-2 -fluorocytidine 5 -diphosphate (FCDP) resulted in time-dependent enzyme inactivation, concomitant and stoichiometric loss of all substituents from the ribose moiety, increase in the UV-Vis absorbance of the protein near 320 nm, and... 

Here, the inactivation of ribonucleotide reductase by 2 -deoxy-2 -chlorocytidine and by 2 -deoxy-2 -chlorouridine 5 -diphosphate, as well as by 2 -deoxy-2 -azidocytidine 5 -diphosphate, is described. The results indicate that both B1 and B2 contribute to the active site of the enzyme and that the radical present in B2 directly participates in the catalytic process together with the redox active dithiols of Bl. 

Fritscher J, Artin E, Wnuk S, Bar G, Rohhlee JFI, Kacprzak S, Kaupp M, Griffin RG, Bennati M, Stubbe J. 2005. Structure of the nitrogen-centered radical formed during inactivation of E. coli ribonucleotide reductase by 2 -azido-2 -deox)oiridine-5 -diphosphate Trapping of the 3 -ketonucleotide. J Am Chem Soc 127 7729-7738. 

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