Global conformational changes upon receptor stimulation in photoactive yellow protein

Wouter D. Hoff, Aihua Xie, Ivo H.M. Van Stokkum, Xue jun Tang, Jechiam Gural, Arthur R. Kroon, Klaas J. Hellingwerf*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Abstract

Biological signal transduction starts with the activation of a receptor protein. Two central questions in signaling are the mechanism of activation by a stimulus and the nature and extent of the protein conformational changes involved. We report extensive evidence for the occurrence of large structural changes upon the light activation of photoactive yellow protein (PYP), a eubacterial photosensor. Absorption of a blue photon by the p-coumaric acid (pCA) chromophore in pG, the initial state of PYP, results in the formation of pB, a putative signaling state. In the presence of an adequate hydration shell, large structural changes in the protein backbone, involving both solvent accessible and core regions, were detected using Fourier transform infrared (FTIR) difference spectroscopy. A significant part (23%) of the amide groups which are buried in pG become exposed to the solvent in pB, as measured through light-induced H/D exchange, using both electrospray ionization mass spectrometry and FTIR spectroscopy. Exposure of previously buried hydrophobic sites would lead to an increase in heat capacity during pB formation and a decrease in heat capacity during pB decay. Thermodynamic studies indeed show that the heat capacity change of pB activation is -2.35 ± 0.08 kJ/(mol/K), independent of pH from pH 2.4-7.5. A model for photoactivation of PYP is proposed, which provides a framework for a deeper understanding of receptor activation in general.

Original languageEnglish
Pages (from-to)1009-1017
Number of pages9
JournalBiochemistry
Volume38
Issue number3
Early online date23 Dec 1998
DOIs
Publication statusPublished - 19 Jan 1999

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