Photosystem I charge separation in the absence of centers A and B. I. Optical characterization of center ‘A2’ and evidence for its association with a 64-kDa peptide
Photosystem I charge separation in the absence of centers A and B. I. Optical characterization of center ‘A2’ and evidence for its association with a 64-kDa peptide
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在没有中心 A 和 B 的情况下光系统 I 电荷分离。 I. 中心“A2”的光学表征及其与 64 kDa 肽相关的证据
DOI：
10.1016/0005-2728(86)90091-5
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
J. M. Cornelius
中科院分区：
文献类型：
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作者：
J. Golbeck;J. M. Cornelius
在光系统I亚叶绿体颗粒中加入0.25-2.0%的十二烷基硫酸锂(LDS)后，在698 nm处的闪光诱导吸收瞬变表现出以下特征。(I)对应于P-700+P-430−反向反应的30ms瞬变被1.2ms的瞬变所取代。(Ii)在加入LDS后，瞬变的幅度没有立即改变，但在pH 8.5时半衰期为10min。(3)甲基紫精对瞬变的大小或动力学没有影响，表明它不能接受来自该组分的电子。(4)从400 nm到500 nm的瞬时差谱是铁硫蛋白的特征。(V)在298K到225K之间，该过程遵循一级Arrhenius行为，活化能为13.3kJ/mol，在225K到77K之间，85ms的半衰期保持温度不变。这些性质表明，激光诱导的吸收瞬变对应于在没有还原的电子受体系统的情况下出现的P-700+A−2 Change复合。在LDS存在下，反应中心复合体被解离，允许从含有-kDa P-700的蛋白质中去除较小的肽。随着时间的延长，铁-硫团簇被破坏，通过不稳定的硫化物转化为零价硫。在允许分离小肽的条件下，约有35%的零价硫与-kDa蛋白有关。我们解释了P-700+A−2在加入LDS后的长寿命以及零价硫与一个-kDa蛋白的结合，表明A2与含有P-700的蛋白密切相关，甚至可能是完整的。
The flash-induced absorption transient at 698 nm in a Photosystem I subchloroplast particle showed the following characteristics after addition of 0.25–2.0% lithium dodecyl sulfate (LDS). (i) The 30-ms transient corresponding to the P-700+P-430−backreaction was replaced by a 1.2-ms transient. (ii) The amplitude of the transient did not change immediately after LDS addition, but decayed with a half-life of 10 min at pH 8.5. (iii) Methyl viologen had no effect on the magnitude or kinetics of the transient, indicating that it cannot accept an electron from this component. (iv) The difference spectrum of the transient from 400 nm to 500 nm was characteristic of an iron-sulfur protein. (v) The transient followed first-order Arrhenius behavior between 298 K and 225 K with an activation energy of 13.3 kJ/mol; between 225 K and 77 K, the 85-ms half-time remained temperature-invariant. These properties suggest that the LDS-induced absorption transient corresponds to the P-700+A−2change recombination seen in the absence of a reduced electron-acceptor system. In the presence of LDS, the reaction-center complex was dissociated, allowing removal of the smaller peptides from the 64-kDa P-700-containing protein. With prolonged incubation, the iron-sulfur clusters were destroyed through conversion of the labile sulfide to zero-valence sulfur. About 35% of the zero-valence sulfur was found associated with the 64-kDa protein under conditions that allowed separation of the small peptides. We interpret the long lifetime of the P-700+A−2transient after LDS addition and the association of zero-valence sulfur with a 64-kDa protein to indicate that A2is closely associated with, and perhaps integral with, the P-700-containing protein.