Optical characterization of the immediate electron donor to chlorophyll a + II in O2‐evolving photosystem II complexes Tyrosine as possible electron carrier between chlorophyll a II and the water‐oxidizing manganese complex

FEBS Letters

Schlodder, E.¹  Gerken, S.¹  Brettel, K.¹  Witt, H.T.¹ 

[1] Max-Vollmer-Institut für Biophysikalische und Physikalische Chemie, Technische Universität Berlin, Straße des 17 Juni 135, D-1000 Berlin 12, Germany

关键词: Photosystem II;    P-680;    Tyrosine;    Water oxidation;    Flash absorption spectroscopy;    (Synechococcus sp.);    Chl;    chlorophyll;    D;    component in photosystem II;    characterized by EPR signal IIslow;    Fecy;    K3(Fe(CN)6);    FWHM;    full width at half maximum;    Mes;    4-morpholine-ethanesulphonic acid;    PS II;    photosystem II;    QA;    primary quinone acceptor of PS II;    S;    water-oxidizing enzyme system;    TyrOH;    tyrosine;    Z;    intermediate electron carrier in PS II;    characterized by EPR signal IIvery fast;    ZTris;    electron donor to Chl a + II in PS II inhibited in water oxidation;    characterized by EPR signal IIfast;   

DOI  :  10.1016/0014-5793(88)80174-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The number and chemical nature of the electron carrier(s) between Chl a _II and the water-oxidizing enzyme, S, were analyzed through flash-induced absorption changes in the UV with nanosecond time resolution. (i) At all wavelengths where the reaction of the donor with Chl a ⁺ _II has been characterized, this donor is oxidized in the nanosecond time range in exact accordance with the reduction kinetics of Chl a ⁺ _II. The donor is in turn re-reduced with t > 10,μs, i.e. in the range where S is oxidized. From this time course it is concluded that there exists only one electron carrier between Chl a ⁺ _II and S. (ii) The UV-diference spectrum due to the electron transfer from the immediate donor to Chl a ⁺ _II in the nanosecond time range in O₂-evolving PS II complexes is characterized by a maximum around 260 nm and smaller minimum around 310 nm. This spectrum is identical with that observed for the reaction of the donor with Chl a ⁺ _II in the microsecond time range in Tris-treated PS II. Therefore, the donors in both reactions must be of the same chemical nature. (iii) This result, together with the well-established similarity of EPR signal II_f of the oxidized donor in Tris-treated PS II to the EPR signal III_s, recently assigned to Tyr-160 of the D2 protein of PS II [(1988) Proc. Natl. Acad. Sci. USA 85, 427–430], provides strong evidence that the immediate donor to Chl a ⁺ _II in water-oxidizing PS II is also a tyrosine. (iv) It is shown that the UV-difference spectra of the oxidation of the immediate donor in O₂-evolving as well as that of Tris-treated PS II complexes are similar to the in vitro difference spectrum of the oxidation of tyrosine in water. This independent result supports the conclusion that the donor is a tyrosine.

【 授权许可】

Unknown