Question

Proofreading activity of bacterial DNA polymerase I resides in the __________, and for DNA polymerase III, it's in the __________ subunit.

1) N-terminal domain and epsilon
2) C-terminal domain and tau
3) Central domain and alpha
4) N-terminal domain and beta

Answer 1

The proofreading activity of DNA polymerase I is in the N-terminal domain, while for DNA polymerase III, it's in the epsilon subunit.

Step-by-step explanation:

The proofreading activity of bacterial DNA polymerase I is associated with the N-terminal domain, while for DNA polymerase III, this activity is associated with the epsilon (ε) subunit. When considering DNA replication and the overall fidelity of the process, the proofreading ability of DNA polymerases plays a critical role in ensuring the accuracy of DNA synthesis. This function is integral to the enzymes' ability to correct any errors that may occur during replication by removing incorrectly inserted nucleotides.

Concerning DNA polymerase I, during mild protease treatment, the part of the enzyme that has the 5'→3' exonuclease activity (related to RNA primer removal at the terminal end) can be removed, leaving a fragment known as the Klenow fragment which maintains polymerization and proofreading activities. For DNA polymerase III, the holoenzyme is responsible for most of the DNA replication in prokaryotes and its proofreading ability lies in the epsilon subunit.

Proofreading for DNA polymerase I is in the N-terminal domain, and for DNA polymerase III, it's in the epsilon subunit.