Biophysics

Unraveling Another Sleeve

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Science  26 Nov 2004:
Vol. 306, Issue 5701, pp. 1439
DOI: 10.1126/science.306.5701.1439a

Green fluorescent protein (GFP), along with its natural and synthetic relatives, has become a workhorse of the cell biologist because it emits a bright signal that reveals the locations of molecules or changes in calcium or proton concentration. Dietz and Rief have brought another emerging technology to bear, that of atomic force microscopy (AFM), to explore the potential for using GFP as a sensor of force. To begin with, they have spliced GFP into well-characterized protein constructs in order to grab onto its N- and C-termini. Applying force produces a rather complex relation of force to extension, but an analysis based on theory and simulation provides a three-stage description (with two metastable intermediates) of GFP unfolding. First, the N-terminal α helix detaches from the intact β-stranded barrel core and unwinds; second, a β strand is peeled off of the barrel (like prying loose a stave); and this then results in unfolding of the rest of the molecule. — GJC

Proc. Natl. Acad. Sci. U.S.A. 101, 16192 (2004).

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