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Updated: May 14, 2026

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
Published on: September 27, 2024
Kinetic mechanism of DNA translocation by the RSC molecular motor
Allen Eastlund1, Shuja Shafi Malik, Christopher J Fischer
1Department of Physics and Astronomy, University of Kansas, 1251 Wescoe Hall Dr., 1082 Malott Hall, Lawrence, KS 66045, USA.
Abstract:
ATP-dependent nucleosome repositioning by chromatin remodeling enzymes requires the translocation of these enzymes along the nucleosomal DNA. Using a fluorescence stopped-flow assay we monitored DNA translocation by a minimal RSC motor and through global analysis of these time courses we have determined that this motor has a macroscopic translocation rate of 2.9 bp/s with a step size of 1.24 bp. From the complementary quantitative analysis of the associated time courses of ATP consumption during DNA translocation we have determined that this motor has an efficiency of 3.0 ATP/bp, which is slightly less that the efficiency observed for several genetically related DNA helicases and which likely results from random pausing by the motor during translocation. Nevertheless, this motor is able to exert enough force during translocation to displace streptavidin from biotinylated DNA. Taken together these results are the necessary first step for quantifying both the role of DNA translocation in nucleosome repositioning by RSC and the efficiency at which RSC couples ATP binding and hydrolysis to nucleosome repositioning.
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