Studies on early events of photosynthetic electron transport---functions of Fe,Ca and M

1.用水稻和菠菜的放氧制剂研究了Ca参与光系统II（PS II）电子传递的数量和功能。(1)PS II释氧膜含有两个Ca/PS II，这是异质性的结合亲和力。一个松散结合的钙可以溶解洗涤剂处理和所得到的PS II复合物只含有一个钙是高度活跃的放氧。因此，PS II电子传递只需要一个结合Ca。(2)PS II制剂与高浓度的NaCl处理不溶解钙，即使治疗导致了强失活的氧气释放和恢复所失去的活性通过添加钙。(3)在pH 3.0的一个简短的治疗，这导致释放的两个Cabound PS II膜之一，未能提取钙从PS II复合物含有一个钙，但诱导钙可逆失活的氧释放。这表明不需要酸可提取的Ca ...更多信息 艾德测氧释放。(4)外在的23 kDa的蛋白质被发现，以减少pH 3.0处理的PS II制剂的钙的结合亲和力。(5)上述结果与以下观点不一致：NaCl和pH 3.0处理通过提取结合的Ca抑制氧释放，并且23 kDa蛋白质稳定或保护PS II制剂中的Ca。相反，对NaCl和pH 3.0处理的制剂中氧气释放的Ca浓度依赖性的详细研究强烈表明，这两种处理具有共同的失活机制，即，氧释放复合物的构象变化。交联实验表明，外源性33 kDa蛋白位于chl结合47 kDa蛋白附近，33 kDa蛋白的结合保护Mn免受碱性pH处理。从嗜热蓝细菌S中纯化PS Ⅱ反应中心复合物和D1-D2-细胞色素b559复合物。结果表明，除了细胞色素b559的血红素铁和位于Q_A和Q_B附近的非血红素铁外，还含有一个功能未知的铁原子。少

1. The number and function of Ca involved in photosystem II (PS II) electron transport were studied with oxygen evolving preparations isolated from rice and spinach. (1) PS II oxygen evolving membranes contained two Ca per PS II, which are heterogenous in binding affinity. A loosely bound Ca could be solubilized by detergent-treatments and the resulting PS II complexes containing only one Ca were highly active in oxygen evolution. Thus only one bound Ca is needed for PS II electron transport. (2) Treatment of PS II preparations with high concentrations of NaCl did not solubilize Ca, even though the treatment resulted in a strong inactivation of oxygen evolution and the lost activity was restored by added Ca. (3) A brief treatment at pH 3.0, which caused liberation of one out of the two Cabound to PS II membranes, failed to extract Ca from PS II complexes containing one Ca but induced Ca-reversible inactivation of oxygen evolution. This indicates that the acid-extractable Ca is not need … More ed for oxygen evolution. (4) The extrinsic 23 kDa protein was found to decrease the binding affinity of added Ca to pH 3.0- treated PS II preparations. (5) The above results are inconsistent with the view that NaCl- and pH 3.0-treatments inhibit oxygen evolution by extracting bound Ca and that the 23 kDa protein stabilizes or protects Ca in PS II preparation. Instead, detailed investigation on Ca concentration dependence of oxygen evolution in NaCl- and pH 3.0-treated preparations strongly suggest that the two treatments share a common mechanism of inactivation,i.e., a conformational change of the oxygen evolving complex.2. Crosslinking experiments showed that the extrinsic 33 kDa protein is located near the chlbinding 47 kDa protein and the association of the 33 kDa protein protects Mn against alkaline pH-treatment.3. Purified PS II reaction center complexes and D1-D2-cytochrome b559 complexes from the thermophilic cyanobacterium S. elongatus were found to contain one iron atom of unknown function in addition to a heme iron of cytochrome b559 and a non-heme iron locating near Q_A and Q_B. Less