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Updated: Jul 1, 2026
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Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG
Published on: July 26, 2024
Cellular replisomes are powered by flex-fuel motors for unwinding DNA
Fahad Rashid1, Sushil Pangeni2,3, Chuan Liu1
1Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Nature Communications
|June 29, 2026
Summary
Escherichia coli DnaB helicase is a fast DNA translocase, moving rapidly along single-stranded DNA. This enzyme and its loader can utilize various nucleotide triphosphates (rNTPs/dATP) for DNA unwinding, aiding replication under stress.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA replication requires helicases to unwind DNA.
- Previous studies suggested replicative helicases are slow motors limited by nucleotide turnover.
- The Escherichia coli (E. coli) DnaB helicase is crucial for DNA replication.
Purpose of the Study:
- To investigate the translocation speed and processivity of the E. coli DnaB helicase.
- To determine the nucleotide requirements for DnaB loading and translocation.
- To explore the nucleotide flexibility of replicative helicases.
Main Methods:
- Single-molecule assays to measure DnaB translocation speed and processivity.
- Biochemical experiments to test nucleotide hydrolysis and utilization by DnaB and its loader DnaC.
- Comparative analysis with eukaryotic CMG helicase.
Main Results:
- E. coli DnaB is a fast (3 knt/s), processive translocase, exceeding replisome speed.
- DnaB translocation is resistant to force and high salt concentrations.
- DnaB loader (DnaC) and DnaB itself can utilize various rNTPs and dATP for loading and translocation.
- This nucleotide flexibility extends to the eukaryotic CMG helicase.
Conclusions:
- Replicative helicases are highly adaptable motors with broad nucleotide utilization.
- This indiscriminate nucleotide usage may provide a survival advantage during nucleotide pool stress.
- The study redefines the capabilities of DNA unwinding engines in cellular replication.
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