Steric constraint in the primary photoproduct of sensory rhodopsin II is a prerequisite for light-signal transfer to HtrII

Motohiro Ito, Yuki Sudo, Yuji Furutani, Takashi Okitsu, Akimori Wada, Michio Homma, John L. Spudich, Hideki Kandori

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Sensory rhodopsin II (SRII, also called pharaonis phoborhodopsin, ppR) is responsible for negative phototaxis in Natronomonas pharaonis. Photoisomerization of the retinal chromophore from all-trans to 13-cis initiates conformational changes in the protein, leading to activation of the cognate transducer protein (HtrII). We previously observed enhancement of the C 14-D stretching vibration of the retinal chromophore at 2244 cm -1 upon formation of the K state and interpreted that a steric constraint occurs at the C14D group in SRIIK. Here, we identify the counterpart of the C14D group as Thr204, because the C14-D stretching signal disappeared in T204A, T204S, and T204C mutants as well as a C14-HOOP (hydrogen out-of-plane) vibration at 864 cm-1. Although the K state of the wild-type bacteriorhodopsin (BR), a light-driven proton pump, possesses neither 2244 nor 864 cm-1 bands, both signals appeared for the K state of a triple mutant of BR that functions as a light sensor (P200T/V210Y/A215T). We found a positive correlation between these vibrational amplitudes of the C14 atom at 77 K and the physiological phototaxis response. These observations strongly suggest that the steric constraint between the C14 group of retinal and Thr204 of the protein is a prerequisite for light-signal transduction by SRII.

Original languageEnglish
Pages (from-to)6208-6215
Number of pages8
JournalBiochemistry
Volume47
Issue number23
DOIs
Publication statusPublished - Jun 10 2008
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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