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Biophys. J. BioFAST: First Published June 23, 2006. doi:10.1529/biophysj.106.088344
© 2006 by the Biophysical Society.

A more recent version of this article appeared on September 1, 2006.
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BIOPHYSICAL LETTERS

Urea-induced unfolding of the immunity protein Im9 monitored by spFRET

Tomoko Tezuka-Kawakami 1, Chris Gell 2, David J Brockwell 2, Sheena E Radford 2 and D. Alastair Smith 2*

1 University Of Leeds
2 University of Leeds

* To whom correspondence should be addressed. E-mail: d.a.m.smith{at}leeds.ac.uk.

Submitted on May 3, 2006
Revised on May 22, 2006
Accepted on 16 June 2006


  Abstract
We have studied the urea-induced unfolding of the E colicin immunity protein Im9 using diffusion single-pair fluorescence resonance energy transfer. Detailed examination of the proximity ratio of the native and denatured molecules over a wide range of urea concentrations suggests that the conformational properties of both species is denaturant- dependent. While native molecules become gradually more expanded as urea concentration increases, denatured molecules show a dramatic dependence of the relationship between proximity ratio and denaturant concentration, consistent with substantial compaction of the denatured ensemble at low denaturant concentrations. Analysis of the widths of the proximity ratio distributions for each state suggests that whilst the native state ensemble is relatively narrow and homogeneous, the denatured state may possess heterogeneity in mildly denaturing conditions.

Key Words: FRET, denatured, folding, immunity protein, single molecule, urea




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E. Sherman, A. Itkin, Y. Y. Kuttner, E. Rhoades, D. Amir, E. Haas, and G. Haran
Using Fluorescence Correlation Spectroscopy to Study Conformational Changes in Denatured Proteins
Biophys. J., June 15, 2008; 94(12): 4819 - 4827.
[Abstract] [Full Text] [PDF]


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Copyright © 2006 by the Biophysical Society.