High-fidelity DNA sensing by protein binding fluctuations

Area of Science:

• Molecular Biology
• Biophysics
• Biochemistry

Background:

• RecA protein is crucial for DNA repair, initiating the SOS response by binding to damaged single-stranded DNA.
• Understanding the precise mechanisms of DNA recognition and length discrimination by RecA is vital for comprehending cellular repair pathways.

Purpose of the Study:

• To investigate how RecA protein discriminates between different lengths of single-stranded DNA.
• To elucidate the role of adenosine triphosphate (ATP) consumption in RecA's DNA binding dynamics and length sensing capabilities.

Main Methods:

• Utilizing fluorescence anisotropy measurements to observe RecA-DNA interactions at the binding onset.
• Developing a theoretical model to explain the observed DNA length sensing based on binding fluctuations.

Main Results:

• RecA protein exhibits enhanced discrimination of DNA length upon consumption of adenosine triphosphate (ATP).
• DNA length sensing by RecA is explained by out-of-equilibrium binding fluctuations, analogous to microtubule dynamic instability.
• The binding fluctuation cascade architecture generalizes the kinetic proofreading mechanism.

Conclusions:

• Out-of-equilibrium fluctuations and irreversible multistage pathways enhance biological system precision in noisy environments.
• RecA's mechanism provides a model for how biological systems achieve high fidelity in molecular recognition.
• ATP consumption is a key factor in RecA's ability to accurately sense DNA length for effective SOS response.