X-ray radiation induces deprotonation of the bilin chromophore in crystalline D. radiodurans phytochrome

J Am Chem Soc. 2015 Mar 4;137(8):2792-5. doi: 10.1021/ja510923m. Epub 2015 Feb 18.


We report that in the red light-absorbing (Pr) state, the bilin chromophore of the Deinococcus radiodurans proteobacterial phytochrome (DrBphP) is hypersensitive to X-ray photons used in typical synchrotron X-ray protein crystallography experiments. This causes the otherwise fully protonated chromophore to deprotonate without additional major structural changes. These results have major implications for our understanding of the structural and chemical characteristics of the resting and intermediate states of phytochromes and other photoreceptor proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bile Pigments / chemistry*
  • Crystallography, X-Ray
  • Deinococcus*
  • Molecular Dynamics Simulation
  • Phytochrome / chemistry*
  • Protein Conformation
  • Protons*
  • X-Rays / adverse effects


  • Bacterial Proteins
  • Bile Pigments
  • Protons
  • Phytochrome