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Photochemical characterization of actinorhodopsin and its functional existence in the natural host

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Title: Photochemical characterization of actinorhodopsin and its functional existence in the natural host
Authors: Nakamura, Shintaro Browse this author
Kikukawa, Takashi Browse this author →KAKEN DB
Tamogami, Jun Browse this author
Kamiya, Masakatsu Browse this author
Aizawa, Tomoyasu Browse this author
Hahn, Martin W. Browse this author
Ihara, Kunio Browse this author
Kamo, Naoki Browse this author
Demura, Makoto Browse this author
Keywords: Actinorhodopsin
Light-driven proton pump
Flash photolysis
Microbial rhodopsin
Issue Date: Dec-2016
Publisher: Elsevier
Journal Title: Biochimica et Biophysica Acta (BBA) Bioenergetics
Volume: 1857
Issue: 12
Start Page: 1900
End Page: 1908
Publisher DOI: 10.1016/j.bbabio.2016.09.006
PMID: 27659506
Abstract: Actinorhodopsin (ActR) is a light-driven outward H+ pump. Although the genes of ActRs are widely spread among freshwater bacterioplankton, there are no prior data on their functional expression in native cell membranes. Here, we demonstrate ActR phototrophy in the native actinobacterium. Genome analysis showed that Candidatus Rhodoluna planktonica, a freshwater actinobacterium, encodes one microbial rhodopsin (RpActR) belonging to the ActR family. Reflecting the functional expression of RpActR, illumination induced the acidification of the actinobacterial cell suspension and then elevated the ATP content inside the cells. The photochemistry of RpActR was also examined using heterologously expressed RpActR in Escherichia coli membranes. The purified RpActR showed lambda(max) at 534 nm and underwent a photocycle characterized by the very fast formation of M intermediate. The subsequent intermediate, named P-620, could be assigned to the 0 intermediate in other H+ pumps. In contrast to conventional 0, the accumulation of P620 remains prominent, even at high pH. Flash-induced absorbance changes suggested that there exists only one kind of photocycle at any pH. However, above pH 7, RpActR shows heterogeneity in the H+ transfer sequences: one first captures H+ and then releases it during the formation and decay of P-650, while the other first releases H+ prior to H+ uptake during P-620 formation. (C) 2016 Elsevier B.V. All rights reserved.
Rights: ©2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Type: article (author version)
Appears in Collections:生命科学院・先端生命科学研究院 (Graduate School of Life Science / Faculty of Advanced Life Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 菊川 峰志

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