Analysis of molecular mechanisms to control two electron transfer directions in photosynthetic reaction centers

2015 Fiscal Year Final Research Report

• Project/Area Number: 24570183
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Biophysics
• Research Institution: Osaka University
• Principal Investigator: Oh-oka Hirozo 大阪大学, 理学(系)研究科(研究院), 准教授 (30201966)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: 光合成 / 反応中心 / 緑色イオウ細菌 / ヘリオバクテリア / ホモダイマー / 光化学系I / フーリエ赤外分光法 / 電子スピン共鳴

Outline of Final Research Achievements

We mutated PscA-Leu688 and PscA-Val689 to cysteine residues in the green sulfur bacteriumChlorobaculum tepidum; these residues were predicted to interact with the special pair P840, based on sequence comparison with PS I. Light-induced Fourier transform infrared difference measurements showed that the L688C mutation induced a differential signal of the S-H stretching vibration in the P840+/P840 spectrum, as reported in P800+/P800 difference spectrum in a heliobacterial RC. This suggests that there is a common spatial configuration around the special pair sites among type 1 RCs.
We identified a new transient electron spin-polarized electron paramagnetic resonance (ESP-EPR) signal, arising from the radical pair of the oxidized electron donor and the reduced electron acceptor (P800+ MQ－), in the heliobacterial RC (hRC) core complex. The result revealed the quinone usage as the secondary electron acceptor in hRC, as in the case of PS I.

Free Research Field

生物物理