DNA Polymerase III Holoenzyme of Escherichia Coli: An Asymmetric Dimeric Replicative Complex Containing Distinguishable Leading and Lagging Strand Polymerases

Abstract

The DNA polymerase III holoenzyme is the major replicative enzyme in Escherichia coli (for a review see ref. 1). A final definition of the enzyme’s structure has not yet been accomplished, but it is apparent that it contains at least seven different subunits: α, ε, θ, β, δ, γ and τ (2–4). The holoenzyme contains a catalytic core, termed DNA polymerase III, composed of the α, ε and θ subunits. DNA polymerase III can catalyze limited synthesis in short gaps created by nuclease treatment of duplex DNA, but it is inactive in reconstituted natural Escherichia coli replication systems (3, 5).