The β Sliding Clamp of E. coli DNA Polymerase III Holoenzyme Balances Opposing Functions
The β subunit of E. coli DNA polymerase III holoenzyme (pol III holoenzyme) anchors this multiprotein chromosomal replicase to DNA for fast and highly processive replication (Kornberg and Baker 1991; Stukenberg et al. 1991). Its ring shape (Fig. 1) allows it to completely encircle DNA while freely diffusing along the duplex (Stukenberg et al. 1991; Kong et al. 1992). The β “sliding clamp” confers onto pol III holoenzyme a high degree of processivity (50kb; Fay et al. 1981) and a rapid speed of synthesis (750 nucleotides/s; O’Donnell and Kornberg 1985) which results from the continual proximity of the polymerase and DNA through their mutual association with β (Stukenberg et al. 1991).
KeywordsHydrolysis Hydrocarbon Polypeptide Beach Triphosphate
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