Photocurrent and Electronic Activities of Oriented-His-Tagged Photosynthetic Light-Harvesting/Reaction Center Core Complexes Assembled onto a Gold Electrode

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• 作者：Masaharu Kondo ; Kouji Iida ; Takehisa Dewa ; Hirofumi Tanaka ; Takuji Ogawa ; Sakiko Nagashima ; Kenji V. P. Nagashima ; Keizo Shimada ; Hideki Hashimoto ; Alastair T. Gardiner ; Richard J. Cogdell ; Mamoru Nango
• 刊名：Biomacromolecules
• 出版年：2012
• 出版时间：February 13, 2012
• 年：2012
• 卷：13
• 期：2
• 页码：432-438
• 全文大小：443K
• 年卷期：v.13,no.2(February 13, 2012)
• ISSN：1526-4602

文摘

A polyhistidine (His) tag was fused to the C- or N-terminus of the light-harvesting (LH1)-伪 chain of the photosynthetic antenna core complex (LH1-RC) from Rhodobacter sphaeroides to allow immobilization of the complex on a solid substrate with defined orientation. His-tagged LH1-RCs were adsorbed onto a gold electrode modified with Ni-NTA. The LH1-RC with the C-terminal His-tag (C-His LH1-RC) on the modified electrode produced a photovoltaic response upon illumination. Electron transfer is unidirectional within the RC and starts when the bacteriochlorophyll a dimer in the RC is activated by light absorbed by LH1. The LH1-RC with the N-terminal His-tag (N-His LH1-RC) produced very little or no photocurrent upon illumination at any wavelength. The conductivity of the His-tagged LH1-RC was measured with point-contact current imaging atomic force microscopy, indicating that 60% of the C-His LH1-RC are correctly oriented (N-His 63%). The oriented C-His LH1-RC or N-His LH1-RC showed semiconductive behavior, that is, had the opposite orientation. These results indicate that the His-tag successfully controlled the orientation of the RC on the solid substrate, and that the RC produced photocurrent depending upon the orientation on the electrode.