Final answer:
The proofreading activities of E. coli DNA polymerases, particularly DNA polymerase III, involve the removal of incorrect nucleotides during DNA replication through 3' exonuclease activity, which occurs at the enzyme's exonuclease domain.
Step-by-step explanation:
Understanding the Proofreading Function of E. coli DNA Polymerases
Proofreading activities of E. coli DNA polymerases are a crucial aspect of DNA replication, ensuring the accuracy of the process. These enzymes carry out their function by reading the newly added base and confirming its correct pairing with the template strand. If an incorrect pairing is detected, DNA polymerase III, which is the enzyme primarily responsible for DNA synthesis in E. coli, exhibits 3' exonuclease activity that allows it to remove the incorrect nucleotide. The proofreading occurs at the exonuclease domain where the enzyme makes a cut at the phosphodiester bond of the incorrect nucleotide and then replaces it with the correct one.
It's interesting to note that DNA polymerase I also shows proofreading activity; however, it is involved primarily in excising RNA primers from the lagging strand during replication and filling in the gaps with DNA. Arthur Kornberg's discovery of DNA polymerase in E. coli and subsequent discoveries by his offspring not only revealed the mechanisms of replication but also underscored the importance of proofreading to the fidelity of DNA replication.