Regulation mechanism of direction of the proton translocation in proteorhodopsin

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K18519
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Functional biochemistry
• Research Institution: Matsuyama University
• Principal Investigator: TAMOGAMI JUN 松山大学, 薬学部, 助教 (30580089)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 生体エネルギー変換 / 微生物型ロドプシン / レチナール / フォトサイクル / プロトン移動

Outline of Final Research Achievements

The purpose of this study is to clarify the molecular mechanism of reverse of direction of the proton translocation under alkaline conditions in proteorhodopsin (PR), a light-driven proton pump from marine eubacteria. From the analysis of the photocycle and accompanying proton transfer under alkaline conditions, a parallel photocycle, during which a M-like photointermediate (Ma) is formed, was observed in addition to a photocycle at neutral pH. The photocycle via Ma at alkali pH was accompanied by the sequence and direction of the photoinduced proton transfer opposite to neutral pH. Moreover, we observed that the cytoplasmic transmembrane region in PR is already hydrophilic at the dark state through the bleach reaction by hydroxylamine.

Free Research Field

生物物理化学

Academic Significance and Societal Importance of the Research Achievements

本研究による結果から、微生物型ロドプシンのプロトン輸送の方向を決める機構は何かという本質的な問題を考える上での１つの役立つ情報が得られたものと考える。さらに、海洋でのエネルギー合成が主な役割であるとこれまで考えられてきたPRに別の機能も存在する可能性があるという問題も提起し、近年見つかってきている内向きプロトンポンプ型の微生物型ロドプシンの生理的な機能を考える上でも重要な情報を提供するものと考えている