Chloride‐depletion of photosynthetic water oxidase

[摘要]

Chloride depletion blocks the normal four-step progress of photosynthetic water oxidation. We studied proton release in chloride-depleted thylakoids which were dark-adapted and excited by flashing light. Proton release was blocked from the second flash on, possibly leaving an uncompensated positive charge in the catalytic centre. The reduction of P⁺ ₆₈₀ by Tyr_z was still very rapid (⪡ 10 μs). From the third flash on, P⁺ ₆₈₀ was reduced more slowly (), and by an electrogenic back-reaction. The uncompensated positive charge may be the reason why the rapid reduction of P⁺ ₆₈₀ by Tyr_z is prevented and the transmembrane charge-pair recombination is facilitated.

[学科分类] 生物化学/生物物理

[关键词] Photosynthesis;Water oxidation;Chloride;Proton;Electrochromism;P680 reduction;BBY;PS II enriched membrane fragments;BSA;bovine serum albumin;Chl;chlorophyll;DMBQ;2;6 dimethyl-p-benzoquinone;DNP-INT;dinitrophenylether of iodonitrothymol;EDTA;ethylene diamine tetraacetic acid;EPR;electron paramagnetic resonance;NR;neutral red;PS I;II;photosystem I;II;P680;primary electron donor of PS II;P700;primary electron donor of PS I;Si;ith oxidation state of water oxidase according to the Kok-model in controls and;Si ∗;in thylakoids perturbed by chloride deficiency;XANES;X-ray absorption near edge structure