Question

The Mg^2+ ion in restriction endonuclease is not bound to ________

(a) Water molecule

(b) Carboxylates of the enzymes aspertate group

(c) Oxygen

(d) Histidine

I got this question in a national level competition.

This question is from Restriction Endonuclease topic in division Genomics : The Mapping and Sequencing of Genomes of Cytogenetics

Answer 1

Correct answer is (d) Histidine

The explanation is: In restriction endonucleases we don’t have His as a ligand to the central metal ion Mg^2+. While it’s binding to the other groups assists in the nucleophilic attack.