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Functional Integration of the Bacteriophage T4 DNA Replication Complex: The Multiple Roles of the ssDNA Binding
Claire S Albrecht1,2,3, Brett Israels1,2,4, Jack Maurer1,2,4
1Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403, United States.
Biochemistry
|December 8, 2025
Summary
Single-stranded DNA binding protein (gp32) regulates T4 phage DNA replication. Its C-terminal domains (CTDs) are crucial for initiating protein assembly at DNA junctions, with strand polarity significantly influencing this process.
Area of Science:
- Molecular Biology
- Biophysics
- Virology
Background:
- Single-stranded DNA binding protein (gp32) is essential for T4 bacteriophage DNA replication.
- Gp32 coordinates replication by binding and sliding on single-stranded DNA.
- The role of gp32's disordered C-terminal domains (CTDs) in filament nucleation at DNA junctions is unclear.
Purpose of the Study:
- To investigate the initial steps of gp32 assembly on DNA junctions.
- To define the molecular steps and energy landscapes of gp32 cluster formation.
- To elucidate the role of CTDs in gp32 nucleation and filament dynamics.
Main Methods:
- Microsecond-resolved single-molecule Förster resonance energy transfer (smFRET).
- Studies on gp32 assembly on short oligo-deoxythymidine single strands near ss-dsDNA junctions.
- Analysis of free energy surfaces for gp32 cluster initiation.
Main Results:
- Gp32 nucleation and regulatory interactions at ss-dsDNA junctions are strongly influenced by DNA strand polarity.
- Identified molecular steps and free energy landscapes for gp32 cluster formation.
- Provided evidence for the role of CTDs in orienting gp32 monomers at junctions.
Conclusions:
- The C-terminal domains (CTDs) of gp32 play a critical role in initiating and regulating gp32-ssDNA filament formation at junctions.
- Strand polarity is a key determinant of gp32 binding and assembly dynamics.
- A model is proposed for CTD function in facilitating non-base-sequence-specific binding during phage DNA replication.
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