Ribonucleotide reductase and deoxyribonucleotide pools.

Ribonucleotide reductase plays a crucial role in the maintenance of dNTP pools. A molecular model for the allosteric regulation of the enzyme is substantiated by the effects of nucleosides or inhibitors on pool sizes in intact cells as well as by manifestations of mutations of the reductase and other enzymes involved in deoxynucleoside metabolism. Studies of the dynamics of dNTP pools in 3T6 cells suggest compartmentation of dCTP pools, with perferential DNA synthesis from a pool labeled from cytidine. In contrast, no kinetic evidence for more than one dTTP pool was obtained. Our experiments also suggest that all dTTP formed in growing 3T6 cells is used up for DNA synthesis.