PMID:10662672
| Citation |
George, H, Kuraoka, I, Nauman, DA, Kobertz, WR, Wood, RD and West, SC (2000) RuvAB-mediated branch migration does not involve extensive DNA opening within the RuvB hexamer. Curr. Biol. 10:103-6 |
|---|---|
| Abstract |
The Escherichia coli RuvA and RuvB proteins promote the branch migration of Holliday junctions during the late stages of homologous recombination and DNA repair (reviewed in [1]). Biochemical and structural studies of the RuvAB-Holliday junction complex have shown that RuvA binds directly to the Holliday junction [2] [3] [4] [5] [6] and acts as a specificity factor that promotes the targeting of RuvB [7] [8], a hexameric ring protein that drives branch migration [9] [10] [11]. Electron microscopic visualisation of the RuvAB complex revealed that RuvA is flanked by two RuvB hexamers, which bind DNA arms that lie diametrically opposed across the junction [8]. ATP-dependent branch migration occurs as duplex DNA is pumped out through the centre of each ring. Because RuvB possesses well-conserved helicase motifs and RuvAB exhibits a 5'-3' DNA helicase activity in vitro [12], the mechanism of branch migration is thought to involve DNA opening within the RuvB ring, which provides a single strand for the unidirectional translocation of the protein along DNA. We have investigated whether the RuvB ring can translocate along duplex DNA containing a site-directed interstrand psoralen crosslink. Surprisingly, we found that the crosslink failed to inhibit branch migration. We interpret these data as evidence against a base-by-base tracking model and suggest that extensive DNA opening within the RuvB ring is not required for DNA translocation by RuvB. |
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| Keywords |
Adenosine Triphosphate/metabolism; Bacterial Proteins/chemistry; Bacterial Proteins/physiology; Biopolymers; DNA/chemistry; DNA/genetics; DNA Helicases; DNA Repair; DNA-Binding Proteins/physiology; Escherichia coli Proteins; Hydrolysis; Recombination, Genetic |
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