Ca2+ binding to the oxygen evolving enzyme varies with the redox state of the Mn cluster

FEBS Letters

Boussac, Alain¹  Rutherford, A.William¹ 

[1] Service de Biophysique, Departement de Biologie, CEN de Saclay, 91191 Gif-sur-Yvette, France

关键词: Photosynthesis;    Photosystem II;    Oxygen evolution;    Ca2+;    Water oxidase;    PS II;    Photosystem II;    PPBQ;    phenyl parabenzoquinone;    Chl;    chlorophyll;   

DOI  :  10.1016/0014-5793(88)80071-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Oxygen evolution by the mangano-enzyme of photosystem II is inhibited by Ca²⁺ depletion induced by NaCl washing and restored by Ca²⁺ addition. The effectiveness of NaCl treatment in inhibiting oxygen evolution in photosystem II was studied after a series of preilluminating flashes. The susceptibility of the enzyme to NaCl treatment varied with the number of preilluminating flashes and this variation showed an oscillation pattern with a period of four. This pattern is characteristic of cycling through the four long-lived intermediate states in the enzyme cycle (i.e. the states, S₀, S₁, S₂, S₃). The relative extent of inhibition corresponding to each of the S states was as follows: S₃ > S₀≈S₂ > S₁. From these results it is concluded that Ca²⁺ binding is dependent on the S states and that Ca²⁺ probably plays a fundamental role in the mechanism of water splitting. The results also help to explain the conflicting reports of the extent of inhibition induced by NaCl washing and the controversy over which electron transfer step is inhibited by Ca²⁺ depletion.

【 授权许可】

Unknown