RecQ periodically patrols on the 5′-ssDNA.
A, the 5′-partial duplex 47 nt 17 bp contains a 17 bp duplex and a 47 nt 5′-ssDNA. B, the typical FRET traces of 47 nt 17 bp in 5 nm RecQ and indicated ATP concentrations. C, FRET distributions of 47 nt 17 bp only and in 5 nm RecQ and different concentrations of ATP. D, a proposed action of RecQ on the 5′-partial duplex. E, the typical FRET traces of 47 nt 17 bp in 5 nm RecQ523 and indicated ATP concentrations. F, FRET distributions of 47 nt 17 bp in 5 nm RecQ, RecQ523, and RecQY555A with 2 mm ATP. G, the fractions of DNA at looping states (FRET > 0.75) in different reaction conditions. H, the number of FRET bursts within the 20-s time window in 5 nm RecQ, RecQ523, and RecQY555A with indicated ATP concentration.