FTIR evidence that the PsbP extrinsic protein induces protein conformational changes around the oxygen-evolving Mn cluster in photosystem II.
FTIR evidence that the PsbP extrinsic protein induces protein conformational changes around the oxygen-evolving Mn cluster in photosystem II.
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DOI：
10.1021/bi9006308
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发表时间：
2009-07
期刊：
影响因子：
2.9
通讯作者：
M. Tomita;K. Ifuku;F. Sato;T. Noguchi
中科院分区：
文献类型：
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作者：
M. Tomita;K. Ifuku;F. Sato;T. Noguchi
光系统II（PSII）的外源蛋白通过控制不可缺少的辅因子Ca（2+）和Cl（-）的结合特性来调节Mn簇上进行的放氧反应。然而，这种调节的分子机制还不清楚。我们已经研究了外部蛋白质PsbO，PsbP，和PsbQ的高等植物与Mn簇的结构耦合，使用傅里叶变换红外光谱（FTIR）。利用菠菜PSII膜测量了S（1）-> S（2）转变的光诱导FTIR差谱，并研究了选择性去除外源蛋白的影响。通过NaCl洗涤去除PsbP和PsbQ蛋白质显示酰胺I带的明显变化，羧酸盐和咪唑基团的带没有明显变化，而通过CaCl（2）洗涤去除所有三种蛋白质没有引起进一步的变化。通过用PsbP重构NaCl洗涤的PSII来恢复原始酰胺I特征，并且用（13）C标记的PsbP观察到相同的恢复。这些结果表明，PsbP蛋白，而不是PsbQ和PsbO，影响周围的Mn簇在内在蛋白质的蛋白质构象，而不改变配体结构。重建与Delta 15-PabP，其中15个N-末端残基被截断，没有恢复酰胺I带，表明N-末端区域的相互作用诱导的构象变化。这一观察结果与先前的发现很好地相关，即Delta 15-PabP在重新结合PSII时不能恢复Ca（2+）和Cl（-）的保留能力[Ifuku，K.，等（2005）Photosynth. Res. 84，251-255]。因此，证据有力地表明，蛋白质构象周围的Mn簇诱导的PsbP通过其N-末端区域的变化影响的Ca（2+）和Cl（-）的结合性能，并提高其保留。
Extrinsic proteins of photosystem II (PSII) regulate the oxygen-evolving reaction performed at the Mn cluster by controlling the binding properties of the indispensable cofactors Ca(2+) and Cl(-). However, the molecular mechanism underlying this regulation is not yet understood. We have investigated the structural couplings of the extrinsic proteins PsbO, PsbP, and PsbQ of higher plants with the Mn cluster using Fourier transform infrared (FTIR) spectroscopy. Light-induced FTIR difference spectra upon the S(1) --> S(2) transition were measured using spinach PSII membranes, and the effects of the selective depletion of extrinsic proteins were examined. Depletion of the PsbP and PsbQ proteins by NaCl washing revealed clear changes in the amide I bands with no appreciable changes in the bands of carboxylate and imidazole groups, whereas the depletion of all three proteins by CaCl(2) washing did not cause further changes. The original amide I features were recovered by reconstitution of the NaCl-washed PSII with PsbP, and the same recovery was observed with (13)C-labeled PsbP. These results indicate that the PsbP protein, but not PsbQ and PsbO, affects the protein conformation around the Mn cluster in the intrinsic proteins without changing the ligand structure. Reconstitution with Delta15-PabP, in which the 15 N-terminal residues were truncated, did not restore the amide I bands, indicating that the interaction of the N-terminal region induces the conformational changes. This observation correlates well with a previous finding that Delta15-PabP did not restore the Ca(2+) and Cl(-) retention ability upon rebinding to PSII [Ifuku, K., et al. (2005) Photosynth. Res. 84, 251-255]. Therefore, the evidence strongly suggests that protein conformational changes around the Mn cluster induced by PsbP through its N-terminal region affect the binding properties of Ca(2+) and Cl(-) and enhance their retention.