Photo‐accumulation of the P+QB − radical pair state in purple bacterial reaction centres that lack the QA ubiquinone

FEBS Letters

McKibbin, Craig²  Jones, Michael R²  Goodwin, Matthew G¹  Wakeham, Marion C² 

[1]Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2UH, UK

[2]Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK

关键词: Reaction centre;    Photosynthesis;    Electron transfer;    Inactive branch;    Mutagenesis;    Spectroscopy;    B;    accessory bacteriochlorophyll;    BChl;    bacteriochlorophyll;    BPhe or H;    bacteriopheophytin;    P;    primary donor of electrons;   

DOI  :  10.1016/S0014-5793(03)00270-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Photo-excitation of membrane-bound Rhodobacter sphaeroides reaction centres containing the mutation Ala M260 to Trp (AM260W) resulted in the accumulation of a radical pair state involving the photo-oxidised primary electron donor (P). This state had a lifetime of hundreds of milliseconds and its formation was inhibited by stigmatellin. The absence of the Q_A ubiquinone in the AM260W reaction centre suggests that this long-lived radical pair state is P⁺Q_B ⁻, although the exact reduction/protonation state of the Q_B quinone remains to be confirmed. The blockage of active branch (A-branch) electron transfer by the AM260W mutation implies that this P⁺Q_B ⁻ state is formed by electron transfer along the so-called inactive branch (B-branch) of reaction centre cofactors. We discuss how further mutations may affect the yield of the P⁺Q_B ⁻ state, including a double alanine mutation (EL212A/DL213A) that probably has a direct effect on the efficiency of the low yield electron transfer step from the anion of the B-branch bacteriopheophytin (H_B ⁻) to the Q_B ubiquinone.

【 授权许可】

Unknown