Very fast electron transfer from cytochrome to the bacterial photosynthetic reaction center at low temperature

FEBS Letters

Dohse, Barbara¹  Oesterhelt, Dieter¹  Mathis, Paul²  Ortega, José M² 

[1] Max-Planck Institut für Biochemie, 82152 Martinsried, Germany;Section de Bioénergétique (CNRS, URA 1290), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France

关键词: Electron transfer;    Cytochrome;    Reaction center;    Low temperature;    Water in proteins;    Rhodopseudomonas viridis;    E h;    redox potential of medium;    E m;    midpoint redox potential;    P;    primary electron donor;    QA;    primary quinone acceptor;    RC;    reaction center;    WT;    wild type strain;   

DOI  :  10.1016/S0014-5793(96)01440-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Electron transfer from the proximal heme c-559 to the primary donor P has been studied in reaction centers of the photosynthetic bacterium Rhodopseudomonas viridis in which the tyrosine residue L162 was replaced by threonine. In the wild type, when the two high-potential hemes of the tetraheme cytochrome are reduced before flash excitation, a rapid electron transfer (t _1/2=190 ns) observed at ambient temperature disappears below 190 K. In the mutant, the reaction is partly maintained down to 8 K, leading to irreversible charge separation. The reaction rate is nearly temperature-independent between 294 K and 8 K (t _1/2≈450 ns). The different behavior of wild type and mutant reaction centers is attributed to differences in a network of water molecules, the freezing of which may block structural reorganizations associated with cytochrome oxidation, in the wild type but not in the mutant.

【 授权许可】

Unknown