A phylogenetically distinctive and extremely heat stable light-driven proton pump from the eubacterium Rubrobacter xylanophilus DSM 9941 T

Kanae Kanehara, Susumu Yoshizawa, Takashi Tsukamoto, Yuki Sudo

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Rhodopsins are proteins that contain seven transmembrane domains with a chromophore retinal and that function as photoreceptors for light-energy conversion and light-signal transduction in a wide variety of organisms. Here we characterized a phylogenetically distinctive new rhodopsin from the thermophilic eubacterium Rubrobacter xylanophilus DSM 9941 T that was isolated from thermally polluted water. Although R. xylanophilus rhodopsin (RxR) is from Actinobacteria, it is located between eukaryotic and archaeal rhodopsins in the phylogenetic tree. Escherichia coli cells expressing RxR showed a light-induced decrease in environmental pH and inhibition by a protonophore, indicating that it works as a light-driven outward proton pump. We characterized purified RxR spectroscopically, and showed that it has an absorption maximum at 541 nm and binds nearly 100% all-Trans retinal. The pK a values for the protonated retinal Schiff base and its counterion were estimated to be 10.7 and 1.3, respectively. Time-resolved flash-photolysis experiments revealed the formation of a red-shifted intermediate. Of note, RxR showed an extremely high thermal stability in comparison with other proton pumping rhodopsins such as thermophilic rhodopsin TR (by 16-Times) and bacteriorhodopsin from Halobacterium salinarum (HsBR, by 4-Times).

Original languageEnglish
Article number44427
JournalScientific Reports
Volume7
DOIs
Publication statusPublished - Mar 14 2017

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Rubrobacter xylanophilus
Eubacteria
rhodopsin
proton pump
heat
Halobacterium
phototransduction
energy conversion
Actinobacteria
photolysis
thermal stability
photoreceptors
protons

ASJC Scopus subject areas

  • General

Cite this

A phylogenetically distinctive and extremely heat stable light-driven proton pump from the eubacterium Rubrobacter xylanophilus DSM 9941 T. / Kanehara, Kanae; Yoshizawa, Susumu; Tsukamoto, Takashi; Sudo, Yuki.

In: Scientific Reports, Vol. 7, 44427, 14.03.2017.

Research output: Contribution to journalArticle

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