The α (alpha), ε (epsilon) and θ (theta) subunits make up the core enzyme to perform polymerization and proofreading.

The γ (gamma) complex is involved in "loading" the enzyme onto the template at the replication fork.

The β (beta) subunit serves as a "clamp" and prevents the core enzyme from falling off the template during polymerization.

The τ (tau) subunit functions to dimerize two core polymerases allowing simultaneous synthesis of both strands of the helix.

The holoenzyme and several other proteins at the replication fork together form a huge complex called the replisome.