Question

Which cation is placed in the catalytic subunit of RNA polymerase?

• A. Zn2+
• B. Mn2+
• C. Mg2+
• D. Fe3+

Answer 1

Answer:

C. Mg2+

Magnesium ion is mandatory for the catalytic action as it shields the negative charge of the phosphate groups of rNTPs and also promotes the nucleophilic attack by the 3’-OH group. Manganese, zinc and iron are part of other biologically important enzymes.