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Circadian clock protein KaiC forms ATP-dependent hexameric rings and binds DNA
Tetsuya Mori1, Sergei V Saveliev, Yao Xu
1Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
Summary
Synechococcus circadian clock protein KaiC forms ATP-dependent hexameric rings. These complexes bind DNA, supporting KaiC
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- KaiC is an essential circadian clock protein in cyanobacteria.
- Sequence analyses suggest KaiC belongs to the RecA/DnaB superfamily, known for DNA-binding homohexamers.
Purpose of the Study:
- To investigate the quaternary structure and DNA-binding capabilities of KaiC.
- To determine if KaiC forms complexes similar to other RecA/DnaB superfamily members.
Main Methods:
- Electron microscopy to visualize KaiC complexes.
- Analytical ultracentrifugation and chromatography to determine complex size.
- DNA-binding assays using forked DNA substrates.
Main Results:
- KaiC forms ring-like hexameric complexes with a central pore.
- Complex formation is dependent on ATP.
- KaiC binds to forked DNA substrates despite lacking canonical DNA-binding motifs.
Conclusions:
- KaiC's structure and DNA-binding properties support its classification within the RecA/DnaB superfamily.
- These findings have implications for understanding KaiC's enzymatic role in the cyanobacterial circadian clock and gene regulation.