Functional and Photochemical Characterization of a Light-Driven Proton Pump from the Gammaproteobacterium Pantoea vagans

Yuki Sudo, Susumu Yoshizawa

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Photoactive retinal proteins are widely distributed throughout the domains of the microbial world (i.e., bacteria, archaea, and eukarya). Here we describe three retinal proteins belonging to a phylogenetic clade with a unique DTG motif. Light-induced decrease in the environmental pH and its inhibition by carbonyl cyanide m-chlorophenylhydrazone revealed that these retinal proteins function as light-driven outward electrogenic proton pumps. We further characterized one of these proteins, Pantoea vagans rhodopsin (PvR), spectroscopically. Visible spectroscopy and high-performance liquid chromatography revealed that PvR has an absorption maximum at 538 nm with the retinal chromophore predominantly in the all-trans form (>90%) under both dark and light conditions. We estimated the pKa values of the protonated Schiff base of the retinal chromophore and its counterion as approximately 13.5 and 2.1, respectively, by using pH titration experiments, and the photochemical reaction cycle of PvR was measured by time-resolved flash-photolysis in the millisecond timeframe. We observed a blue-shifted and a red-shifted intermediate, which we assigned as M-like and O-like intermediates, respectively. Decay of the M-like intermediate was highly sensitive to environmental pH, suggesting that proton uptake is coupled to decay of the M-like intermediate. From these results, we propose a putative model for the photoreaction of PvR.

Original languageEnglish
Pages (from-to)420-427
Number of pages8
JournalPhotochemistry and Photobiology
Volume92
Issue number3
DOIs
Publication statusPublished - May 1 2016

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Biochemistry
  • Medicine(all)

Fingerprint Dive into the research topics of 'Functional and Photochemical Characterization of a Light-Driven Proton Pump from the Gammaproteobacterium Pantoea vagans'. Together they form a unique fingerprint.

  • Cite this