Spectrally silent intermediates during the photochemical reactions of Salinibacter sensory rhodopsin i

Keiichi Inoue, Yuki Sudo, Michio Homma, Hideki Kandori

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Salinibacter sensory rhodopsin I (SrSRI) is a microbial rhodopsin discovered from the eubacterium Salinibacter ruber. It is thought to be a photoreceptor engaging the signal transductions for both positive and negative phototaxis. To elucidate the photoreactions of SrSRI in the presence and absence of chloride ions, we measured the refractive index change after the photoexcitation by the transient grating method. As a result, two spectrally silent processes were identified after the formation of M intermediate, and we named the spectrally identical intermediates M1, M2, and M3. The enthalpy changes (ΔH) were estimated as ΔH = 136, 99, and 63 kJ/mol for K, M1, and M2 intermediates, respectively. The ΔH values were significantly decreased (36-55 kJ/mol) by the removal of chloride ions, suggesting their importance for structural changes of SrSRI. Volume expansions of SrSRI were observed on the spectrally silent steps (44 and 11 mL/mol). They may be related to the signaling process because blue-shifted intermediates of sensory rhodopsins are thought to be active state(s) for phototaxis.

Original languageEnglish
Pages (from-to)4500-4508
Number of pages9
JournalJournal of Physical Chemistry B
Volume115
Issue number15
DOIs
Publication statusPublished - Apr 21 2011

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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