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The phage T4-coded DNA replication helicase (gp41) forms a hexamer upon activation by nucleoside triphosphate
F Dong1, E P Gogol, P H von Hippel
1Department of Chemistry, University of Oregon, Eugene 97403-1229, USA.
The Journal of Biological Chemistry
|March 31, 1995
Summary
Bacteriophage T4 helicase (gp41) forms dimers that assemble into hexamers upon ATP/GTP binding. This DNA helicase structure is crucial for its function in DNA replication.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- The bacteriophage T4 DNA replication helicase (gp41) is essential for viral DNA synthesis.
- Understanding the oligomeric state and assembly of helicases is critical for elucidating DNA replication mechanisms.
Purpose of the Study:
- To investigate the oligomeric state and assembly pathway of the bacteriophage T4 helicase (gp41).
- To determine the structural basis for gp41's function in DNA replication.
Main Methods:
- Sedimentation analysis
- High-performance liquid chromatography (HPLC)
- Cryoelectron microscopy
- Analytical ultracentrifugation
- Protein-protein cross-linking
Main Results:
- gp41 exists primarily as a dimer at physiological concentrations.
- ATP or GTP binding induces dimer assembly into hexameric complexes.
- Hexameric assembly is reversible and dependent on purine nucleotide triphosphatase (PuTP) substrate levels.
- The active hexamer exhibits a hexagonal trimer of asymmetric dimers structure, likely with D3 symmetry.
- Non-hydrolyzable ATP/GTP analogs stabilize the hexameric state.
Conclusions:
- The bacteriophage T4 helicase (gp41) functions as a hexameric complex regulated by nucleotide binding and hydrolysis.
- The structural organization of gp41 into a hexamer is key to its DNA helicase activity.
- These findings provide insights into the broader family of viral and cellular helicases.