DNA Polymerase III Structure
By itself, the polymerase catalytic subunit of the DNA polymerase III holoenzyme (Pol III HE), α, exhibits no special properties that hint of the Pol III HE’s high catalytic efficiency, accuracy, and enormous processivity. These properties are gained by association with other proteins through a series of distinct protein interaction domains. A PHP domain at the N-terminus of Pol III α binds the proofreading subunit, ε. A typical Mg++-dependent polymerase catalytic domain has a fold similar to the DNA polymerase β (Pol X family). Adjacent to the polymerase domain is the β-binding domain. Interaction of this domain with the β2 sliding clamp processivity factor, together with an ε−β2interaction, provides the primary determinants of the enzyme’s processivity. The C-terminus contains two domains, one an OB fold that may bind single-stranded DNA and a τ-binding domain that binds the τ-subunit of the DnaX complex. X-ray crystal structures of Pol III α in the apoenzyme form, bound...
KeywordsPolymerase Domain Exonuclease Domain Catalytic Aspartate Thumb Domain Palm Domain
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