Figure 2.

The action of the three components of the ring-type DNA polymerases. The protein ring (sliding clamp) is assembled onto a primed template junction by a clamp-loader complex in an ATP-driven reaction. The DNA polymerase (Pol) then assembles with the ring on DNA to form a highly processive polymerase, which pulls the ring along behind it during chain extension while remaining tethered to DNA by the ring.