Here's why:
* High processivity: DNA polymerase III can add thousands of nucleotides per second without detaching from the DNA strand. This makes it incredibly efficient for replicating the large E. coli genome.
* 3' to 5' exonuclease activity: This allows DNA polymerase III to "proofread" its work, removing any incorrectly added nucleotides. This helps to maintain the accuracy of DNA replication.
* 5' to 3' polymerase activity: This is the primary function of DNA polymerase III, adding nucleotides to the new DNA strand in a 5' to 3' direction.
While there are other enzymes involved in DNA replication (like DNA polymerase I, which is involved in filling gaps, and helicase, which unwinds the DNA strands), DNA polymerase III is the primary enzyme responsible for synthesizing the majority of the new DNA strand.
