Core subunits of DNA Pol III are
Pol III core minimal replication unit that co-purifies consists of three subunits tightly associated: alpha encoded by dnaE harbors polymerase active site with palm-thumb-fingers architecture binding Mg2+, epsilon encoded by dnaQ provides 3' to 5' exonuclease proofreading through DEDD motif, and theta encoded by holE stabilizes epsilon and enhances fidelity against thermal denaturation. This alpha-epsilon-theta heterotrimer associates with tau and beta to form holoenzyme capable of high processivity. Early models suggesting alpha-beta-gamma composition confused holoenzyme subunits with core de
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: Pol III core subunits alpha, epsilon, theta