Question

Record the effect, on nucleotide end products, of elevated ATP or dATP on its activity. (up, down, or no charge)

Allosteric Effector	[dATP]	[dGTP]	[dCTP]	[dTTP]
ATP
dATP

Then, propose a physiological context for the regulation of ribonucleotide reductase by ATP and dATP. Invoke energy charge in the explanation.

Answer 1

Regulation of Ribonucleotide reductase(RNR)is designed to maintain balanced quantities of dNTP's. Binding of effective molecules either increases or decreases RNR activity.When ATP binds to the allosteric activity site, it activates RNR. In contrast,when dATP binds to this site, it deactivate RNR.

In addition to controlling activities, the allosteric mechanism also regulates the substrate specificity and ensures the enzymes produces an equal amount of each dNTP's for DNA synthesis.

In all classes(I,II and III), binding of ATP or dATP to the allosteric site induces reduction of Cytidine 5'-diphosphate(CDP) and Uridine 5'-diphosphate(UDP); 2'-deoxyguanosine 5'-triphosphate(dGTP) induces reduction of adenosine 5'-diphosphate(ADP); and 2'-deoxythymidine 5'-triphosphate(dTTP) induces reduction of guanosine 5'-diphosphate(GDP).

The Interactions Energy between the enzyme and substrate along the reaction co-ordinate and the substrate steric strain energy have been obtained.

They catalyzes the conversion of ribonucleotides into deoxyribonucleotides, the monomeric precursor of DNA biosynthesis and repair and the protein free radical to activate the substrate..