Question

For which of the following processes, ATP is not required?

• A. Polymerase chain reaction
• B. DNA ligation
• C. Restriction endonuclease digestion
• D. Transcription

Hint:

Molecular Enzyme Cofactors:
Type II Restriction Endonucleases $\rightarrow \text{Mg}^{2+}$ ONLY (No ATP needed).
DNA Ligase (T4) $\rightarrow$ Requires ATP.
E. coli Ligase $\rightarrow$ Requires $\text{NAD}^+$.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Enzymatic phosphodiester cleavage by Type II restriction endonucleases is exergonic and requires only divalent magnesium ($ ext{Mg}^{2+}$) cofactors without ATP hydrolysis.

Step 2: Detailed Explanation:
Energy requirements of molecular biological enzymes:
1. Restriction Endonuclease Digestion (Type II REs): Standard cloning enzymes (e.g., EcoRI, HindIII, BamHI) hydrolyze phosphodiester bonds exergonically; they require only $\text{Mg^{2+}$ ions} and do not require ATP.
2. DNA Ligation: T4 DNA Ligase requires ATP hydrolysis to form phosphodiester bonds.
3. Transcription: RNA Polymerase hydrolyzes ribonucleotide triphosphates (ATP, GTP, CTP, UTP).
4. PCR: Uses dNTPs as building blocks.

Step 3: Final Answer:
Thus, ATP is not required for Restriction endonuclease digestion, corresponding to option (C).