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Updated: Feb 11, 2026

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
Published on: September 27, 2024
A model of DNA unwinding dynamics by the RecBCD complex and its regulation by Chi recognition
1Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Abstract:
The Escherichia coli RecBCD enzyme is a heterotrimeric helicase-nuclease complex responsible for processing of double-stranded DNA breaks for repair by homologous recombination. It is a highly processive, duplex unwinding and degrading motor, with its activities being regulated by the octameric recombination hotspot, Chi, which is read as a single-stranded DNA sequence. Here, a model is presented for DNA unwinding by the RecBCD complex and its regulation by Chi recognition. With the model we study analytically the dynamics of DNA unwinding of both wild-type RecBCD and mutant RecBCDK177Q with the motor function of RecD being inactivated by mutagenesis, giving quantitative explanations of the available single-molecule experimental data. The peculiar features of RecBCD such as large variations of DNA unwinding speed of individual enzymes, sensitivity of unwinding speed of a RecBCD molecule on the change of environment, two translocase or helicase activities of RecBC and RecD, etc., are explained. Furthermore, predicted results are presented.
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