Early structural rearrangements in the photocycle of an integral membrane sensory receptor

Structure. 2002 Apr;10(4):473-82. doi: 10.1016/s0969-2126(02)00736-0.


Sensory rhodopsins are the primary receptors of vision in animals and phototaxis in microorganisms. Light triggers the rapid isomerization of a buried retinal chromophore, which the protein both accommodates and amplifies into the larger structural rearrangements required for signaling. We trapped an early intermediate of the photocycle of sensory rhodopsin II from Natronobacterium pharaonis (pSRII) in 3D crystals and determined its X-ray structure to 2.3 A resolution. The observed structural rearrangements were localized near the retinal chromophore, with a key water molecule becoming disordered and the retinal's beta-ionone ring undergoing a prominent movement. Comparison with the early structural rearrangements of bacteriorhodopsin illustrates how modifications in the retinal binding pocket of pSRII allow subtle differences in the early relaxation of photoisomerized retinal.

Publication types

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

MeSH terms

  • Archaeal Proteins / chemistry*
  • Archaeal Proteins / metabolism
  • Carotenoids / chemistry*
  • Carotenoids / metabolism
  • Crystallography, X-Ray
  • Halorhodopsins*
  • Models, Molecular
  • Natronobacterium / chemistry*
  • Natronobacterium / physiology
  • Photochemistry
  • Protein Structure, Secondary
  • Protein Structure, Tertiary*
  • Sensory Rhodopsins*
  • Spectrum Analysis


  • Archaeal Proteins
  • Halorhodopsins
  • Sensory Rhodopsins
  • sensory rhodopsin II protein, archaeal
  • Carotenoids

Associated data

  • PDB/1FBK
  • PDB/1GU8
  • PDB/1GUE