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Large domain movements upon UvrD dimerization and helicase activation.

Binh Nguyen¹, Yerdos Ordabayev¹, Joshua E Sokoloski¹

¹Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110.

Proceedings of the National Academy of Sciences of the United States of America

|November 1, 2017

Summary

The Escherichia coli UvrD helicase requires dimerization for unwinding duplex DNA. Dimer formation shifts the UvrD 2B subdomain to a closed state, activating its helicase activity.

Keywords:

DNA motors DNA repair conformational heterogeneity single molecule

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Area of Science:

Molecular Biology
Biochemistry
DNA Repair Mechanisms

Background:

Escherichia coli UvrD DNA helicase is crucial for DNA repair.
UvrD monomer translocates ssDNA but requires activation for duplex unwinding.
Activation occurs via dimerization or accessory proteins, but the mechanism is unclear.

Purpose of the Study:

To investigate the mechanism of UvrD helicase activation.
To examine the role of UvrD conformational states in helicase activity.
To understand how dimerization influences UvrD function.

Main Methods:

Single-molecule total internal reflection fluorescence microscopy.
Labeling of UvrD for conformational state analysis.
Monitoring rotational states of the UvrD 2B subdomain.

Main Results:

UvrD monomer 2B subdomain exists in open, closed, and intermediate conformations.
DNA substrate binding shifts UvrD to an inactive open state.
Binding of a second UvrD monomer shifts the 2B subdomain to a closed, active state.
Rep helicase binding does not induce this activation.

Conclusions:

UvrD helicase activity is promoted by dimerization.
Interactions between UvrD subunits alter 2B subdomain conformation, activating helicase function.
Dimerization is essential for efficient duplex DNA unwinding by UvrD.