DNA polymerase III holoenzyme
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DNA polymerase III holoenzyme is the primary enzyme complex involved in prokaryotic DNA replication. The complex has high processivity (i.e. the number of nucleotides added per binding event) and, specicifically referring to the replication of the E.coli genome, works in conjunction with four other DNA ploymerases (Pol I, Pol II, Pol IV, and Pol V). Being the primary holoenzyme involved in replication activity, the DNA Pol III holoenzyme also has proofreading capabilities that correct replication mistakes by means of exonuclease activity working 3'->5'.
Components:
- 2 DNA Pol III enzymes, made up of α, ε, θ subunits.
- the α subunit has polymeration activity.
- the ε subunit has proofreading activity.
- θ subunit has no recognized function yet.
- 2 β units which act as sliding DNA clamps, they keep the polymerase binded to the DNA. It has two subunits.
- 2 τ units which connect the 2 DNA Pol III enzymes.
- 1 γ unit which acts as a clamp loader for the lagging strand Okazaki fragments, helping the two β subunits to form a unit and bind to DNA. The γ unit is made up of 5 γ subunits.