Redox and acid-base characterization of cytochrome b-559 in photosystem II particles.
Redox and acid-base characterization of cytochrome b-559 in photosystem II particles.
复制标题
光系统 II 颗粒中细胞色素 b-559 的氧化还原和酸碱表征。
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
M. Losada
中科院分区：
文献类型：
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作者：
J. M. Ortega;M. Hervás;M. Losada
氧化还原和酸/碱的状态和中点电位的细胞色素B-559已被确定在放氧光系统II（PS II）颗粒在室温下的pH范围从6.5至8.5。在pH 7.5时，新鲜PS II颗粒中约2/3的细胞色素B-559以其还原和质子化（不可自动氧化）的高电位形式存在，约1/3以其氧化和非质子化的低电位形式存在。电位还原滴定表明，质子化的高电位对是pH无关的（E '0，+ 380 mV），而低电位对是非质子化的，在pH 7.6以上是pH无关的（E' 0，pH大于7.6，+ 140 mV），但在该pH以下变成pH依赖性的，斜率为-72 mV/pH单位。此外，有证据表明，在PS II颗粒细胞色素B-559可以循环，根据其建立的氧化还原和酸/碱性质，作为一个能量转换器在两个交替中点电位和两个交替pKa值。在室温下，PS II吸收的红光诱导这些颗粒中的细胞色素B-559还原，该反应被二氯苯二甲基脲完全阻断。
The redox and acid/base states and midpoint potentials of cytochrome b-559 have been determined in oxygen-evolving photosystem II (PS II) particles at room temperature in the pH range from 6.5 to 8.5. At pH 7.5 the fresh PS II particles present about 2/3 of their cytochrome b-559 in its reduced and protonated (non-auto-oxidizable) high-potential form and about 1/3 in its oxidized and non-protonated low-potential form. Potentiometric reductive titration shows that the protonated high-potential couple is pH-independent (E'0, + 380 mV), whereas the low-potential couple is non-protonated and pH-independent above pH 7.6 (E'0, pH greater than 7.6, + 140 mV), but becomes pH-dependent below this pH, with a slope of -72 mV/pH unit. Moreover, evidence is presented that in PS II particles cytochrome b-559 can cycle, according to its established redox and acid/base properties, as an energy transducer at two alternate midpoint potentials and at two alternate pKa values. Red light absorbed by PS II induces reduction of cytochrome b-559 in these particles at room temperature, the reaction being completely blocked by dichlorophenyldimethylurea.