Question

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

Short answer

Answer: The holoenzyme of DNA polymerase III is the complete and fully functional form, consisting of all ten subunits. It is capable of efficiently performing all activities related to DNA replication, such as polymerization, proofreading, clamp loading, and processivity. In contrast, the core enzyme consists of only three subunits (Alpha, Epsilon, and Theta) and possesses polymerization and proofreading activities but lacks the high processivity and clamp loading activity found in the holoenzyme. The functions of the ten subunits of DNA polymerase III are as follows: 1. Alpha (α): main component responsible for polymerization activity. 2. Epsilon (ε): proofreading exonuclease to maintain replication fidelity. 3. Theta (θ): stimulates the proofreading activity of the epsilon subunit. 4. Tau (τ): coordinates the activities of two polymerases on both strands during replication. 5. Gamma (γ): performs a similar function to tau and can substitute it. 6. Delta (δ): involved in DNA clamp loading for the Beta subunit. 7. Delta Prime (δ'): functions together with the delta subunit in clamp loading. 8. Chi (χ): enhances processivity by binding to single-stranded DNA binding proteins. 9. Psi (ψ): stabilizes the interaction between the Tau subunit and other holoenzyme subunits. 10. Beta (β): forms a sliding clamp around the DNA for processive replication.

Step-by-step solution

List the Ten Subunits of DNA Polymerase III

The ten subunits of DNA polymerase III are: 1. Alpha (α) subunit 2. Epsilon (ε) subunit 3. Theta (θ) subunit 4. Tau (τ) subunit 5. Gamma (γ) subunit 6. Delta (δ) subunit 7. Delta Prime (δ') subunit 8. Chi (χ) subunit 9. Psi (ψ) subunit 10. Beta (β) subunit

Describe the Functions of Each Subunit

Here are the functions of the 10 subunits of DNA polymerase III: 1. Alpha (α) subunit: It's the main component responsible for the polymerization activity, meaning it adds deoxyribonucleotides to the growing DNA chain. 2. Epsilon (ε) subunit: It is the proofreading exonuclease that removes wrong bases to maintain fidelity during replication. 3. Theta (θ) subunit: It is thought to stimulate the proofreading activity of the epsilon subunit. 4. Tau (τ) subunit: It helps in dimerization of the enzyme and coordinates the activities of two polymerases on both strands during replication. 5. Gamma (γ) subunit: This subunit performs a similar function to tau and can substitute it. 6. Delta (δ) subunit: It is involved in the DNA clamp loading activity that helps the Beta subunit form a clamp around the DNA. 7. Delta Prime (δ') subunit: It functions together with the delta subunit in the clamp loading process. 8. Chi (χ) subunit: It is involved in enhancing the processivity of the enzyme by binding to single-stranded DNA binding proteins. 9. Psi (ψ) subunit: It helps stabilize the interaction between the Tau subunit and other subunits of the holoenzyme. 10. Beta (β) subunit: It forms a sliding clamp around the DNA and provides a strong interaction between the DNA and the holoenzyme for processive replication.

Differentiate between Holoenzyme and Core Enzyme

Holoenzyme refers to the complete and fully functional form of DNA polymerase III. It consists of all the ten subunits, including the core enzyme and the accessory subunits. The holoenzyme efficiently performs all the activities related to DNA replication, such as polymerization, proofreading, clamp loading, and processivity. On the other hand, the core enzyme consists of only three subunits: Alpha (α), Epsilon (ε), and Theta (θ). The core enzyme possesses polymerization and proofreading activities, but lacks the high processivity and clamp loading activity that is characteristic of the holoenzyme.