Light-induced proton release of phytochrome is coupled to the transient deprotonation of the tetrapyrrole chromophore

142Citations
Citations of this article
95Readers
Mendeley users who have this article in their library.

This article is free to access.

Abstract

The Pr → Pfr phototransformation of the bacteriophytochrome Agp1 from Agrobacterium tumefaciens and the structures of the biliverdin chromophore in the parent states and the cryogenically trapped intermediate Meta-RC were investigated with resonance Raman spectroscopy and flash photolysis. Strong similarities with the resonance Raman spectra of plant phytochrome A indicate that in Agp1 the methine bridge isomerization state of the chromophore is ZZZasa in Pr and ZZEssa in Pfr, with all pyrrole nitrogens being protonated. Photoexcitation of Pr is followed by (at least) three thermal relaxation components in the formation of Pfr with time constants of 230 μs and 3.1 and 260 ms. H2O/D2O exchange reveals kinetic isotope effects of 1.9, 2.6, and 1.3 for the respective transitions that are accompanied by changes of the amplitudes. The second and the third relaxation correspond to the formation and decay of Meta-RC, respectively. Resonance Raman measurements of Meta-RC indicate that the chromophore adopts a deprotonated ZZE configuration. Measurements with a pH indicator dye show that formation and decay of Meta-RC are associated with proton release and uptake, respectively. The stoichiometry of the proton release corresponds to one proton per photoconverted molecule. The coupling of transient chromophore deprotonation and proton release, which is likely to be an essential element in the Pr → Pfr photoconversion mechanism of phytochromes in general, may play a crucial role for the structural changes in the final step of the Pfr formation that switch between the active and the inactive state of the photoreceptor. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.

Cite

CITATION STYLE

APA

Borucki, B., Von Stetten, D., Seibeck, S., Lamparter, T., Michael, N., Mroginski, M. A., … Hildebrandt, P. (2005). Light-induced proton release of phytochrome is coupled to the transient deprotonation of the tetrapyrrole chromophore. Journal of Biological Chemistry, 280(40), 34358–34364. https://doi.org/10.1074/jbc.M505493200

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free