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Updated: Jul 7, 2026
17:03
Direct Observation of Enzymes Replicating DNA Using a Single-molecule DNA Stretching Assay
Published on: March 24, 2010
Using microsecond single-molecule FRET to determine the assembly pathways of T4 ssDNA binding protein onto model DNA
Carey Phelps1,2, Brett Israels1,2, Davis Jose1
1Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403.
Summary
T4 bacteriophage gene product 32 (gp32) binding to DNA involves transient intermediate states. Microsecond single-molecule FRET reveals how gp32 assembles on DNA replication forks.
Area of Science:
- Molecular Biology
- Biophysics
- Biochemistry
Background:
- DNA replication is a rapid and accurate process essential for life.
- T4 bacteriophage's single-stranded DNA binding protein (gp32) is crucial for replication complex assembly.
- Understanding protein dynamics at replication forks is key to DNA synthesis fidelity.
Purpose of the Study:
- To investigate the binding kinetics and mechanisms of T4 gp32 on DNA using single-molecule techniques.
- To identify and characterize transient intermediate states during gp32 assembly on DNA.
- To elucidate the role of these states in the overall DNA replication process.
Main Methods:
- Microsecond time-resolved single-molecule Förster Resonance Energy Transfer (smFRET) measurements.
- Utilizing Cy3/Cy5-labeled primer-template (p/t) DNA constructs.
- Applying multipoint time correlation function analysis to smFRET data.
Main Results:
- Identified distinct protein-bound and unbound states of gp32 on a 15-nt ssDNA lattice.
- Revealed the presence of short-lived intermediate bound states during gp32 assembly.
- Determined the translocation mechanisms and kinetics of gp32 binding pathways.
Conclusions:
- Short-lived intermediate states are critical for the cooperative assembly of gp32 on ssDNA.
- These findings provide insights into the dynamic mechanisms of DNA binding proteins at replication forks.
- The study advances our understanding of DNA replication fidelity and regulation.
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