【摘要】 菠菜的PSⅡ颗粒在pH 6.0、有抗坏血酸钠及甘油存在的条件下,用Triton X-100处理后,经过DEAE-Toyopearl 650S离子交换层析柱分离,可得一个由47 kD,D1,D2及Cyt b559组成的PSⅡ反应中心蛋白复合物.纯化的蛋白质复合物在DPC存在下,具明显的光还原DGIP光化学活性,且在暗及光照条件下显示出SignalⅡ_slow及Signal Ⅱ_fast。低温吸收光谱和荧光光谱表明,复合物中只有叶绿素a存在;用有机溶剂抽提复合物的色素,采用一种灵敏的荧光分析方法并结合分光光度法进行分析,也证实了这点。此复合物有锰的存在,重要的化学成分中Chl a/Pheo a/Cyt b559/Mn原子的摩尔比为:18.4:2:0.8:0.3。这些结果表明;此复合物含有从PSⅡ第二电子供体Z到第一电子受体Q_A的完整光系统Ⅱ电子传递链的所有组分,同时也暗示复合物可能含有锰原子结合部位。为我们（Tang 1985）提出的水裂解系存在于PSⅡ反应中心系之中的观点提供了佐证。更多还原

【Abstract】 During the last few years a number of significant advances have been made in the knowledge of the structure-function relationship of photosystem Ⅱ. Recent studies suggested that the site for the primary photochemistry in PS Ⅱ was located on the D1 and D2 proteins. However, the D1 / D2 / Cyt b559 complex conrained no plastoquinone or Mn. In this paper, a photosystem Ⅱ reaction center complex consisting of 47 kD, D1 and D2 polypeptides and cytochrome b-559 (Fig. 2) was isolated from spinach grana thylakoids by treating with 4% Triton X-100 in the presence of ascorbate and glycerol at acidic pH, followed by ionexchange chromatographic separation using DEAE-Toyopearl 650S. The isolated complex was fairly active in the DCIP photoreduction with DPC (190 μ electron eqivalents per mg chlorophyll per h) (Fig. 5) and exhibited a dark-stable and photo-induced EPR Signal Ⅱ (Fig. 8). The absorption (Fig. 3, 4), fluorescence (Figs 6, 7) spectral properties of 47 kD/ /D1/D2/Cyt b559 indicate that only Chl a is present. The Chi a / Pheo a / Cyt b559 /Mn molar ratio in the complex is 18.4:2.0:0.8:0.3. These results suggest that the protein complex contains the intact PS Ⅱ elecotron transport chain from the secondary electron donor Z to the primary electron acceptor Q_A, and also indicate the possibility that Mnbinding site is located in the protein complex. It provides an evidence for the view that the principal site of water oxidation is associated with the PSⅡ reaction center complex (Tang and Satoh 1985).更多还原