Absorption changes in Photosystem II in the Soret band region upon the formation of the chlorophyll cation radical [PD1PD2].
Absorption changes in Photosystem II in the Soret band region upon the formation of the chlorophyll cation radical [PD1PD2].
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叶绿素阳离子自由基 [PD1PD2] 形成后，Soret 带区域中光系统 II 的吸收变化。
DOI：
10.1007/s11120-023-01049-3
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发表时间：
2023
影响因子：
3.7
通讯作者：
Boussac A
中科院分区：
文献类型：
--
作者：
Boussac A
在 pH 8.6 的贫锰 PSII 核心中测量了由 [PD1PD2]+ 状态（光系统 II (PSII) 光激发时形成的叶绿素阳离子自由基）引起的 Soret 区域中闪光引起的吸收变化。在这些条件下，TyrDisi) 在第一次闪蒸之前被还原，并且ii) 在随后的闪蒸之前被氧化。在野生型PSII中，当TyrD●存在时，与TyrDis未氧化时的第一次闪光相比，在[PD1PD2]+-减-[PD1PD2]差异光谱中观察到额外的信号。附加特征是“W 形”，波谷位于 434 nm 和 446 nm。当 TyrDs 还原时，该特征不存在，但当 (i) TyrDs 物理上不存在（并被苯丙氨酸取代）时或 (ii) 当其氢键组氨酸 (D2-His189) 物理上不存在（被亮氨酸取代）时，该特征就存在。因此，在 434 nm 和 446 nm 处没有双槽特征的简单差异光谱似乎需要还原的 TyrD 周围的天然结构环境及其 H 键合伙伴存在。我们没有发现 W 形差异谱中涉及 PD1、ChlD1、PheD1、PheD2、TyrZ 和 Cytb559heme 的证据。然而，PD2轴His配体的突变体D2-His197Ala的使用表明PD2环境似乎参与了“W形”信号的形成。
Flash-induced absorption changes in the Soret region arising from the [PD1PD2]+state, the chlorophyll cation radical formed upon light excitation of Photosystem II (PSII), were measured in Mn-depleted PSII cores at pH 8.6. Under these conditions, TyrDisi) reduced before the first flash, andii) oxidized before subsequent flashes. In wild-type PSII, when TyrD●is present, an additional signal in the [PD1PD2]+-minus-[PD1PD2] difference spectrum was observed when compared to the first flash when TyrDis not oxidized. The additional feature was “W-shaped” with troughs at 434 nm and 446 nm. This feature was absent when TyrDwas reduced, but was present (i) when TyrDwas physically absent (and replaced by phenylalanine) or (ii) when its H-bonding histidine (D2-His189) was physically absent (replaced by a Leucine). Thus, the simple difference spectrum without the double trough feature at 434 nm and 446 nm, seemed to require the native structural environment around the reduced TyrDand its H bonding partners to be present. We found no evidence of involvement of PD1, ChlD1, PheD1, PheD2, TyrZ, and the Cytb559heme in the W-shaped difference spectrum. However, the use of a mutant of the PD2axial His ligand, the D2-His197Ala, shows that the PD2environment seems involved in the formation of “W-shaped” signal.