Tuning the free-energy landscape of a WW domain by temperature, mutation, and truncation
- Houbi Nguyen*,
- Marcus Jäger‡,§,
- Alessandro Moretto‡,
- Martin Gruebele*,¶,‖,**, and
- Jeffery W. Kelly‡,**
- ¶Departments of Chemistry and Physics, *Center for Biophysics and Computational Biology, and ‖Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801; and ‡Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, MB-12, La Jolla, CA 92037
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Communicated by Jiri Jonas, University of Illinois at Urbana-Champaign, Urbana, IL (received for review November 20, 2002)
Abstract
The equilibrium unfolding of the Formin binding protein 28 (FBP) WW domain, a stable three-stranded β-sheet protein, can be described as reversible apparent two-state folding. Kinetics studied by laser temperature jump reveal a third state at temperatures below the midpoint of unfolding. The FBP free-energy surface can be tuned between three-state and two-state kinetics by changing the temperature, by truncation of the C terminus, or by selected point mutations. FBP WW domain is the smallest three-state folder studied to date and the only one that can be freely tuned between three-state and apparent two-state folding by several methods (temperature, truncation, and mutation). Its small size (28–37 residues), the availability of a quantitative reaction coordinate (φT), the fast folding time scale (10s of μs), and the tunability of the folding routes by small temperature or sequence changes make this system the ideal prototype for studying more subtle features of the folding free-energy landscape by simulations or analytical theory.
Footnotes
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↵ § Present address: Department of Chemistry and Biochemistry, Single Molecule Biophysics Group, University of California, Los Angeles, CA 90095.
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↵ ** To whom correspondence may be addressed. E-mail: gruebele{at}scs.uiuc.edu or jkelly{at}scripps.edu.
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See commentary on page 3555.
- Abbreviation:
- FBP,
- Formin binding protein 28
- Copyright © 2003, The National Academy of Sciences
