Trans/cis (Z/E) photoisomerization of the chromophore of photoactive yellow protein is not a prerequisite for the initiation of the photocycle of this photoreceptor protein

R. Cordfunke, R Kort, A. Pierik, B Gobets, G.-J. Koomen, J W Verhoeven, K J Hellingwerf

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The chromophore of photoactive yellow protein (PYP) (i.e., 4-hydroxycinnamic acid) has been replaced by an analogue with a triple bond, rather than a double bond (by using 4-hydroxyphenylpropiolic acid in the reconstitution, yielding hybrid I) and by a "locked" chromophore (through reconstitution with 7-hydroxycoumarin-3-carboxylic acid, in which a covalent bridge is present across the vinyl bond, resulting in hybrid II). These hybrids absorb maximally at 464 and 443 nm, respectively, which indicates that in both hybrids the deprotonated chromophore does fit into the chromophore-binding pocket. Because the triple bond cannot undergo cis/trans (or E/Z) photoisomerization and because of the presence of the lock across the vinyl double bond in hybrid II, it was predicted that these two hybrids would not be able to photocycle. Surprisingly, both are able. We have demonstrated this ability by making use of transient absorption, low-temperature absorption, and Fourier-transform infrared (FTIR) spectroscopy. Both hybrids, upon photoexcitation, display authentic photocycle signals in terms of a red-shifted intermediate; hybrid I, in addition, goes through a blue-shifted-like intermediate state, with very slow kinetics. We interpret these results as further evidence that rotation of the carbonyl group of the thioester-linked chromophore of PYP, proposed in a previous FTIR study and visualized in recent time-resolved x-ray diffraction experiments, is of critical importance for photoactivation of PYP.

Original languageEnglish
Pages (from-to)7396-401
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume95
Issue number13
DOIs
Publication statusPublished - 23 Jun 1998

Keywords

  • Bacterial Proteins
  • Chromatiaceae
  • Coumaric Acids
  • Isomerism
  • Magnetic Resonance Spectroscopy
  • Photochemistry
  • Photoreceptor Cells
  • Photoreceptors, Microbial
  • Spectrophotometry, Ultraviolet
  • Spectroscopy, Fourier Transform Infrared
  • Journal Article

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