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Updated: May 25, 2026

An Aquatic Microbial Metaproteomics Workflow: From Cells to Tryptic Peptides Suitable for Tandem Mass Spectrometry-based Analysis
Published on: September 15, 2015
Diversity and functional analysis of proteorhodopsin in marine Flavobacteria
Susumu Yoshizawa1, Akira Kawanabe, Hiroyasu Ito
1Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, Japan. yoshizawa@aori.u-tokyo.ac.jp
Abstract:
Proteorhodopsin (PR) genes are widely distributed among marine prokaryotes and functions as light-driven proton pump when expressed heterologously in Escherichia coli, suggesting that light energy passing through PR may be substantial in marine environment. However, there are no data on PR proton pump activities in native marine bacteria. Here, we demonstrate light-driven proton pump activity (c. 124 H(+) PR(-1) min(-1) ) in recently isolated marine Flavobacteria. Among 75 isolates, 38 possessed the PR gene. Illumination of cell suspensions from all eight tested strains in five genera triggered marked pH drops. The action spectrum of proton pump activity closely matched the spectral distribution of the sea surface green light field. Addition of hydroxylamine to a solubilized membrane fraction shifted the spectrum to a form characteristic of PR photobleached into retinal oxime, indicating that PRs in flavobacterial cell membranes transform the photon dose in incident radiation into energy in the form of membrane potential. Our results revealed that PR-mediated proton transport can create the sufficient membrane potential for the ATP synthesis in native flavobacterial cells.
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