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Effect of Hofmeister cosolutes on the photocycle of photoactive yellow protein at moderately alkaline pH

Paper ID Volume ID Publish Year Pages File Format Full-Text
30636 44494 2013 9 PDF Available
Title
Effect of Hofmeister cosolutes on the photocycle of photoactive yellow protein at moderately alkaline pH
Abstract

The photocycle of photoactive yellow protein was studied by kinetic absorption spectroscopy from below 100 ns to seconds, at moderately alkaline pH, in the presence of high concentrations of various salts. Chemometric analysis combined with multiexponential fit of the flash-induced difference spectra provided evidence for five intermediates, including a spectrally silent form before the final recovery of the parent state, but only three with significantly distinct spectra. The calculated intermediate spectra constituted the input for the following spectrotemporal model fit using a sufficiently complex photocycle scheme with reversible transitions. This yielded the rate coefficients of the molecular transitions, the final spectra and the kinetics of the intermediates. Except for the transition between the two red shifted (early) intermediates (pR1 and pR2) and the final photocycle step, all reactions appeared to be reversible. Kosmotropic and chaotropic cosolutes had a systematic effect on the molecular rate coefficients. The largest effect, associated presumably with the exposure of the hydrophobic interior of the protein, accompanies the transition between the second red-shifted and the first blue-shifted intermediate (pR2 and pB1, respectively), i.e. it coincides with the chromophore protonation. The dependence of the rate coefficients on the Hofmeister cosolutes suggests that the conformational change of photoactive yellow protein leading eventually to the most unfolded signaling state takes place in several steps, and starts already with the relaxation after the chromophore isomerization in the microsecond time domain.

► We studied the PYP photocycle by kinetic spectroscopy in various Hofmeister salts. ► Chemometric analysis and model fit yielded the spectra and kinetics of intermediates. ► Chaotropes stabilize, kosmotropes destabilize the conformationally open pB forms. ► The Hofmeister effect is strongest in the pR2 → pB1, transition rather than in pB1 → pB2. ► The structural opening towards the signaling state takes place gradually, in three steps.

Keywords
Kinetic absorption spectroscopy; Hofmeister effect; Photoactive yellow protein; Conformational change
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Effect of Hofmeister cosolutes on the photocycle of photoactive yellow protein at moderately alkaline pH
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 120, 5 March 2013, Pages 111–119
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us