Spectroscopic studies of a sensory rhodopsin I homologue from the archaeon Haloarcula vallismortis

Jin Yagasaki, Daisuke Suzuki, Kunio Ihara, Keiichi Inoue, Takashi Kikukawa, Makoto Sakai, Masaaki Fujii, Michio Homma, Hideki Kandori, Yuki Sudo

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


Sensory rhodopsin I (SRI) functions as a dual receptor regulating both negative and positive phototaxis. It transmits light signals through changes in protein-protein interactions with its transducer protein, HtrI. The phototaxis function of Halobacterium salinarum SRI (HsSRI) has been well characterized using genetic and molecular techniques, whereas that of Salinibacter ruber SRI (SrSRI) has not. SrSRI has the advantage of high protein stability compared with HsSRI and, therefore, provided new information about structural changes and Cl- binding of SRI. However, nothing is known about the functional role of SrSRI in phototaxis behavior. In this study, we expressed a SRI homologue from the archaeon Haloarcula vallismortis (HvSRI) as a recombinant protein which uses all-trans-retinal as a chromophore. Functionally important residues of HsSRI are completely conserved in HvSRI (unlike in SrSRI), and HvSRI is extremely stable in buffers without Cl-. Taking advantage of the high stability, we characterized the photochemical properties of HvSRI under acidic and basic conditions and observed the effects of Cl- on the protein under both conditions. Fourier transform infrared results revealed that the structural changes in HvSRI were quite similar to those in HsSRI and SrSRI. Thus, HvSRI can become a useful protein model for improving our understanding of the molecular mechanism of the dual photosensing by SRI.

Original languageEnglish
Pages (from-to)1183-1190
Number of pages8
Issue number6
Publication statusPublished - Feb 16 2010
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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