If an alteration occurred in the activity site of the R1 subunit of E.coli ribonucleotide reductase that allowed dATP to bind but precluded ATP binding to the site,a possible result would be that ribonucleotide reductase
A) would remain active under all conditions.
B) would be decreased when dATP bound both the activity and specificity sites.
C) activity would be increased when ATP bound the specificity site.
D) activity would be decreased when dCDP bound the catalytic site.

Question

Quizplus · Accepted Answer

The R1 subunit of E.coli ribonucleotide reductase has two sites - an activity site and a specificity site. The activity site binds to ATP and reduces ribonucleotides, while the specificity site binds to dATP and inhibits the reduction of other nucleotides. If the activity site of the R1 subunit allowed dATP to bind but precluded ATP binding, the enzyme would be unable to reduce ribonucleotides in the presence of dATP. As a result, the activity of ribonucleotide reductase would be decreased when dATP bound both the activity and specificity sites. Therefore, option B is the correct answer. Options A, C, and D are incorrect as they do not explain the effect of the alteration on the activity of ribonucleotide reductase.

If an Alteration Occurred in the Activity Site of the R1