| Autor: |
Shlyk O; The Weizmann Institute of Science, Department of Plant and Environmental Sciences, 76100 Rehovot, Israel., Samish I; The Weizmann Institute of Science, Department of Plant and Environmental Sciences, 76100 Rehovot, Israel., Matěnová M; University of South Bohemia in České Budějovice, Faculty of Science, 37005 České Budějovice, Czech Republic., Dulebo A; University of South Bohemia in České Budějovice, Faculty of Science, 37005 České Budějovice, Czech Republic., Poláková H; University of South Bohemia in České Budějovice, Faculty of Science, 37005 České Budějovice, Czech Republic., Kaftan D; University of South Bohemia in České Budějovice, Faculty of Science, 37005 České Budějovice, Czech Republic.; Institute of Microbiology CAS, Department of Phototrophic Microorganisms, 37981 Trebon, Czech Republic., Scherz A; The Weizmann Institute of Science, Department of Plant and Environmental Sciences, 76100 Rehovot, Israel. |
| Abstrakt: |
Interquinone Q A - → Q B electron-transfer (ET) in isolated photosystem II reaction centers (PSII-RC) is protein-gated. The temperature-dependent gating frequency "k" is described by the Eyring equation till levelling off at T ≥ 240 °K. Although central to photosynthesis, the gating mechanism has not been resolved and due to experimental limitations, could not be explored in vivo. Here we mimic the temperature dependency of "k" by enlarging V D1-208 , the volume of a single residue at the crossing point of the D1 and D2 PSII-RC subunits in Synechocystis 6803 whole cells. By controlling the interactions of the D1/D2 subunits, V D1-208 (or 1/T) determines the frequency of attaining an ET-active conformation. Decelerated ET, impaired photosynthesis, D1 repair rate and overall cell physiology upon increasing V D1-208 to above 130 Å 3 , rationalize the >99% conservation of small residues at D1-208 and its homologous motif in non-oxygenic bacteria. The experimental means and resolved mechanism are relevant for numerous transmembrane protein-gated reactions. |
