Visualizing reaction pathways in photoactive yellow protein from nanoseconds to seconds

Hyotcherl Ihee*, Sudarshan Rajagopal, Vukica Srajer, Reinhard Pahl, Spencer Anderson, Marius Schmidt, Friedrich Schotte, Philip A. Anfinrud, Michael Wulff, Keith Moffat

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

232 Scopus citations


Determining 3D intermediate structures during the biological action of proteins in real time under ambient conditions is essential for understanding how proteins function. Here we use time-resolved Laue crystallography to extract short-lived intermediate structures and thereby unveil signal transduction in the blue light photoreceptor photoactive yellow protein (PYP) from Halorhodospira halophila. By analyzing a comprehensive set of Laue data during the PYP photocycle (forty-seven time points from one nanosecond to one second), we track all atoms in PYP during its photocycle and directly observe how absorption of a blue light photon by its p-coumaric acid chromophore triggers a reversible photocycle. We identify a complex chemical mechanism characterized by five distinct structural intermediates. Structural changes at the chromophore in the early, red-shifted intermediates are transduced to the exterior of the protein in the late, blue-shifted intermediates through an initial "volume-conserving" isomerization of the chromophore and the progressive disruption of hydrogen bonds between the chromophore and its surrounding binding pocket. These results yield a comprehensive view of the PYP photocycle when seen in the light of previous biophysical studies on the system.

Original languageEnglish (US)
Pages (from-to)7145-7150
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number20
StatePublished - May 17 2005


  • Intermediates
  • Mechanism
  • Signal transduction
  • Singular value decomposition
  • Time-resolved crystallography

ASJC Scopus subject areas

  • General


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