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Updated: Jan 22, 2026
09:45
Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
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The transitional kinetics between open and closed Rep structures can be tuned by salt via two intermediate states
Jamieson A L Howard1, Benjamin Ambrose2, Mahmoud A S Abdelhamid2
1School of Physics, Engineering and Technology, University of York, York YO10 5DD, UK.
Nucleic Acids Research
|January 21, 2026
Summary
Superfamily 1A DNA helicase Rep undergoes conformational changes, revealing hidden intermediates crucial for DNA replication, repair, and recombination. Salt concentration influences the stability of these states, impacting enzyme function.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- DNA helicases are essential enzymes that unwind DNA, but their dynamic conformational changes are not well understood.
- The Rep helicase (superfamily 1A) plays a critical role in bacterial DNA replication, repair, and recombination processes.
Purpose of the Study:
- To investigate the structural dynamics and conformational transitions of the single-molecule DNA helicase Rep.
- To identify and characterize intermediate states during the Rep helicase's conformational cycle.
Main Methods:
- Utilized time-correlated single-photon counting (TCSPC) and fluorescence correlation spectroscopy (FCS).
- Employed rapid single-molecule Förster resonance energy transfer (smFRET) and Anti-Brownian ELectrokinetic (ABEL) trapping.
- Integrated molecular dynamics simulations (MDS) for high-resolution analysis of domain movements.
Main Results:
- Identified four distinct conformational states of Rep, including two previously uncharacterized intermediates (S2, S3) between open (S1) and closed (S4) states.
- Demonstrated that the stability of these states is dependent on salt concentration.
- Elucidated the multi-step conformational switch mechanism (S1→S2→S3→S4) involving coordinated movements of all four subdomains (1A, 1B, 2A, 2B).
Conclusions:
- The Rep helicase utilizes conformational plasticity to explore various structures, regulated by salt concentration, before DNA binding.
- The S1→S2 transition dynamics suggest a mechanism to prevent premature closure in the absence of DNA.
- Findings support a general binding model for accessory DNA helicases involving salt-tunable conformational landscapes.
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