Temperature Dependency of Proton Pumping Activity for Marine Microbial Rhodopsin from Antartic Ocean

Se-Hwan Kim,Soon Gyu Hong,Byunghoon Jung,Kwang-Hwan Jung

doi:10.1038/s41598-020-58023-5

Se-Hwan Kim, Soon Gyu Hong + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-58023-5

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Abstract

Proteorhodopsin (PR) is discovered from marine bacteria and it has proton pumping activity from inside to outside of the cell using light energy. In general, PR classified into two groups by the maximum absorption spectra. In this study, we isolated the two of a full sequence of opsin homologues by PCR from the seawater sample near King George Island, Antarctica. One was the same sequence as the first reported GPR (Green-light absorbing PR) from Monterey Bay. Another named HSG119 was a newly discovered sequence which shows high sequence similarity with BPR (Blue-light absorbing PR). HSG119 has an absorption maximum at 493 nm with broader spectrum at pH7.0 and it can pump protons out of the cell membrane. Interestingly, it showed a similar temperature dependence to GPR(Y200N) that isolated near the North pole.

Highlights

Type I rhodopsins have been well studied as a model system, which makes a chemical gradient from light energy or contributed to phototaxis of host cell[6]
Only green-light absorbing proteorhodopsin (GPR) type PRs were found at the Arctic Ocean, but GPR and blue-light absorbing proteorhodopsin (BPR) types were identified on the surface from the Antarctic ocean
PRs from Arctic and Antarctic Ocean are well-known in terms of their sequences and absorption maxima[8,13,14,22]

Summary

Introduction

Type I rhodopsins have been well studied as a model system, which makes a chemical gradient from light energy or contributed to phototaxis of host cell[6]. One is Asp[97] as proton acceptor and another is Glu[108] as proton donor against the chromophore Schiff base in GPR (Green-light absorbing ProteoRhodopsin). In another type I rhodopsin, bacteriorhodopsin (BR), Asp[85] and Asp[96] work similar function, respectively[16,18]. The absorption maximum peak of PRs shows variability depends on the places where their host is living. NPR8 from the sea near the Korea Arctic Research Station Dasan at NyAlesund, Svalbard, Norway showed a different temperature dependency between GPR and BPR21. We isolated new BPR type gene from Antarctic Ocean and it was characterized by using several biophysical methods such as light-driven proton pumping assays, and absorption spectroscopy, laser flash-induced photolysis technique

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