Question

List and describe the function of the ten subunits constituting DNA polymerase III. Distinguish between the holoenzyme and the core enzyme.

Answer 1

DNA polymerase III in prokaryotes consists of ten subunits with specific functions. The holoenzyme and core enzyme are different forms of the polymerase complex.

Step-by-step explanation:

The DNA polymerase III in prokaryotes is composed of ten subunits, each with its own function.

1. α subunit: Responsible for assembly of the polymerase on the DNA template.
2. ε subunit: Involved in proofreading and editing the newly synthesized DNA.
3. θ subunit: Stabilizes the DNA polymerase complex.
4. τ subunit: Acts as a clamp loader to load the β sliding clamp onto the DNA.
5. γ complex: Coordinates the movement of the DNA polymerase and helicase during replication.
6. β subunit: Forms a sliding clamp that helps the DNA polymerase stay attached to the DNA template during replication.
7. δ subunit: Functions in processivity, helping the DNA polymerase move along the DNA template.
8. ψ subunit: Binds to the ε subunit and enhances its proofreading activity.
9. DnaX complex: Consisting of the γ complex and the τ and δ subunits, it is involved in loading the β sliding clamp onto the DNA template.
10. o subunit: Involved in termination of DNA replication.

The holoenzyme refers to the DNA polymerase III complex composed of all ten subunits, while the core enzyme refers to the complex consisting of the four subunits α, a, ß, and ß'. The core enzyme alone is capable of synthesizing DNA, but the holoenzyme is more efficient and stable, especially during processive replication.