Evidence from Chlamydomonas on the photoactivation of rhodopsins without isomerization of their chromophore

Kenneth W. Foster, Jureepan Saranak, Sonja Krane, Randy L. Johnson, Koji Nakanishi

Research output: Contribution to journalArticle

4 Scopus citations


Attachment of retinal to opsin forms the chromophore N-retinylidene, which isomerizes during photoactivation of rhodopsins. To test whether isomerization is crucial, custom-tailored chromophores lacking the β-ionone ring and any isomerizable bonds were incorporated in vivo into the opsin of a blind mutant of the eukaryote Chlamydomonas reinhardtii. The analogs restored phototaxis with the anticipated action spectra, ruling out the need for isomerization in photoactivation. To further elucidate photoactivation, responses to chromophores formed from naphthalene aldehydes were studied. The resulting action spectral shifts suggest that charge separation within the excited chromophore leads to electric field-induced polarization of nearby amino acid residues and altered hydrogen bonding. This redistribution of charge facilitates the reported multiple bond rotations and protein rearrangements of rhodopsin activation. These results provide insight into the activation of rhodopsins and related GPCRs.

Original languageEnglish (US)
Pages (from-to)733-742
Number of pages10
JournalChemistry and Biology
Issue number6
StatePublished - Jun 24 2011


ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Molecular Biology
  • Clinical Biochemistry
  • Molecular Medicine
  • Pharmacology

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