Absorption changes in Photosystem II in the Soret band region upon the formation of the chlorophyll cation radical [P D1 P D2 ] +
Absorption changes in Photosystem II in the Soret band region upon the formation of the chlorophyll cation radical [P D1 P D2 ] +
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叶绿素阳离子自由基形成后索雷带区域光系统 II 的吸收变化 [P D1 P D2 ]
DOI：
10.1101/2022.05.12.491653
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Boussac A
中科院分区：
文献类型：
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作者：
Boussac A
在光激发光系统II(PSII)形成的叶绿素阳离子自由基[PD1PD2]+态引起的Soret区，在pH 8.6时测量了闪光诱导的吸收变化。在这些条件下，TyrDisi)在第一次闪光之前还原，Andii)在随后的闪光之前氧化。在野生型PSII中，当tyrd存在时，与TyrD未被氧化时的第一次闪光相比，在[PD1PD2]+-负-[PD1PD2]差谱中观察到了额外的信号。另外一个特征是在434 nm和446 nm处有低谷的“W”字形。当TyrD被还原时，这一特征不存在，但在(I)当TyrD物理上不存在(并被苯丙氨酸取代)或(Ii)当其氢键组氨酸(D2-His189)物理上不存在(由亮氨酸取代)时存在。因此，在434 nm和446 nm处没有双谷特征的简单差异光谱似乎需要还原的TyrD及其氢键伙伴周围的自然结构环境存在。我们没有发现PD1、ChlD1、PheD1、PheD2、TyrZ和Cytb559heme参与W型差异谱的证据。然而，使用PD2轴His配体的突变体D2-His197Ala，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.