Figure 5. Binding of UvsX to dsDNA in the presence of increasing amounts of homologous ssDNA.

A) 2 µM UvsX (final concentration) was added to a mixture of 2 µM dsDNA (dT₂₅:dA₂₂XA₂ oligo 2:oligo 1), 2.5 mM ATP, and various amounts of homologous ssDNA (dA_25, oligo 4). The amplitude of fluorescence quenching was graphed as a function of ssDNA concentration and fit to a single exponential function (solid line) to demonstrate the trend. B) Schematic of strand exchange reaction used to determine if strand exchange is occurring during the monitoring of binding reactions depicted in A. C) Strand exchange reaction containing 0 or 2 µM UvsX, 8 µM ssDNA (dA₂₅) and 2 µM ³²-P labeled dsDNA (dA₂₅:dT₂₅) in the presence on 2.5 mM ATP. Control lane “C” indicated where on the gel the outgoing strand would be seen if strand exchange were to occur.