Publication Date:
2013-05-29
Description:
A complex of the three ( α ) core subunits and the β 2 sliding clamp is responsible for DNA synthesis by Pol III, the Escherichia coli chromosomal DNA replicase. The 1.7 Å crystal structure of a complex between the PHP domain of α (polymerase) and the C-terminal segment of (proofreading exonuclease) subunits shows that is attached to α at a site far from the polymerase active site. Both α and contain clamp-binding motifs (CBMs) that interact simultaneously with β 2 in the polymerization mode of DNA replication by Pol III. Strengthening of both CBMs enables isolation of stable α : β 2 complexes. Nuclear magnetic resonance experiments with reconstituted α : β 2 demonstrate retention of high mobility of a segment of 22 residues in the linker that connects the exonuclease domain of with its α -binding segment. In spite of this, small-angle X-ray scattering data show that the isolated complex with strengthened CBMs has a compact, but still flexible, structure. Photo-crosslinking with p -benzoyl-L-phenylalanine incorporated at different sites in the α -PHP domain confirm the conformational variability of the tether. Structural models of the α : β 2 replicase complex with primer-template DNA combine all available structural data.
Print ISSN:
0305-1048
Electronic ISSN:
1362-4962
Topics:
Biology
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