Yamagishi A, Katoh S
Arch Biochem Biophys. 1983 Sep;225(2):836-46. doi: 10.1016/0003-9861(83)90096-6.
The reaction center of photosystem 2 has been highly purified from digitonin-solubilized thylakoid membranes of the thermophilic cyanobacterium Synechococcus sp. by means of sucrose density gradient centrifugation and electrophoresis on polyacrylamide gels containing digitonin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of isolated reaction center complex yielded four chlorophyll a proteins named CP2-a, CP2-b, CP2-c, and CP2-d. When reelectrophoresed, CP2-a was transformed to CP2-d, and CP2-b was converted to CP2-a and CP2-d. The reaction center complex consisted of two major polypeptides of 47,000 and 40,000 Da and several minor polypeptides. CP2-b contained a 47,000-Da polypeptide together with 66,000- and 31,000-Da polypeptides, while CP2-a and CP2-d had only a 47,000-Da polypeptide. The apoprotein of CP2-c was a 40,000-Da polypeptide. Absorption spectra of CP2-a, -b, and -d were similar to each other but distinctly different from those of CP2-c at liquid nitrogen temperature. The reaction center complex showed two fluorescence emission bands at 686 and 694 nm at 77 degrees K. CP2-a, -b, and -d emitted the band at 694 nm, whereas the fluorescence peak at 686 nm was associated with CP2-c. It is concluded that the photosystem 2 reaction center complex contains two chlorophyll-binding subunits, CP2-d (or CP2-a) which may be the site of the primary photochemistry of photosystem 2 and CP2-c which may function as the antenna of the reaction center of photosystem 2.
通过蔗糖密度梯度离心以及在含有洋地黄皂苷的聚丙烯酰胺凝胶上进行电泳，从嗜热蓝藻聚球藻属经洋地黄皂苷增溶的类囊体膜中高度纯化出了光系统2的反应中心。对分离出的反应中心复合物进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳，得到了四种叶绿素a蛋白，分别命名为CP2-a、CP2-b、CP2-c和CP2-d。再次电泳时，CP2-a转变为CP2-d，CP2-b转变为CP2-a和CP2-d。反应中心复合物由两条主要的多肽（分子量分别为47,000和40,000道尔顿）以及几条次要的多肽组成。CP2-b包含一条47,000道尔顿的多肽以及66,000道尔顿和31,000道尔顿的多肽，而CP2-a和CP2-d仅含有一条47,000道尔顿的多肽。CP2-c的脱辅基蛋白是一条40,00道尔顿的多肽。在液氮温度下，CP2-a、-b和-d的吸收光谱彼此相似，但与CP2-c的吸收光谱明显不同。反应中心复合物在77K时显示出686和694纳米处的两个荧光发射带。CP2-a、-b和-d在694纳米处发射该带，而686纳米处的荧光峰与CP2-c相关。得出的结论是，光系统2反应中心复合物包含两个叶绿素结合亚基，CP2-d（或CP2-a）可能是光系统2初级光化学的位点，而CP2-c可能作为光系统2反应中心的天线发挥作用。
