Modified molecular interactions of the pheophytin and plastoquinone electron acceptors in photosystem II of chlorophyll d-containing Acaryochloris marina as revealed by FTIR spectroscopy
Modified molecular interactions of the pheophytin and plastoquinone electron acceptors in photosystem II of chlorophyll d-containing Acaryochloris marina as revealed by FTIR spectroscopy
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DOI：
10.1007/s11120-014-0073-x
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发表时间：
2015-01
影响因子：
3.7
通讯作者：
Yuko Sano;Kaichiro Endo;T. Tomo;T. Noguchi
中科院分区：
文献类型：
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作者：
Yuko Sano;Kaichiro Endo;T. Tomo;T. Noguchi
无氯蓝藻是一种独特的蓝藻，其主要色素为叶绿素(Chl)。由于Chld的激发能量比普通光合作用生物体中的Chlad小，因此光系统的能量是OFA。码头一直是人们感兴趣的主题。已有研究表明，光系统II(PSII)的氧化还原活性植酸酶(PHEO)和初级质醌电子受体(QA)的氧化还原电位(Em‘s)。Marina高于含有Chla的PSII，以补偿Chld较小的激发能量(Allakhverdiev等人，Proc Natl Acad Sci USA 107：3924-3929,2010；同上。108：8054-8058,2011)。为了阐明这些酶的作用机制，在本研究中，我们研究了Pheo和QA在PSII核心复合体中的分子相互作用。用傅里叶变换红外(FTIR)光谱分析。Pheo和QA一次还原的光致傅里叶变换红外光谱表明，Pheo的酮和酯的C=O伸缩和氯环振动以及QA−的半喹酮阴离子Ina的CO/CC伸缩区域的光谱特征。Marina与含有Chla的蓝藻的相应光谱有显著不同。这些观察结果表明，这些辅因子的分子相互作用，包括C=O基团的氢键相互作用，在它们与PSII蛋白的结合部位发生了修饰。根据这些结果，结合D_1和D_2蛋白的序列信息，我们认为这是一种可能。通过改变附近的氢键网络来改变这些辅因子的结合口袋的结构，从而改变Pheo和QA的Em。
Acaryochloris marinais a unique cyanobacterium that contains chlorophyll (Chl)das a major pigment. Because Chldhas smaller excitation energy than Chlaused in ordinary photosynthetic organisms, the energetics of the photosystems ofA. marinahave been the subject of interest. It was previously shown that the redox potentials (Em’s) of the redox-active pheophytina(Pheo) and the primary plastoquinone electron acceptor (QA) in photosystem II (PSII) ofA. marinaare higher than those in Chla-containing PSII, to compensate for the smaller excitation energy of Chld(Allakhverdiev et al., Proc Natl Acad Sci USA 107: 3924–3929, 2010; ibid. 108: 8054–8058, 2011). To clarify the mechanisms of theseEmincreases, in this study, we have investigated the molecular interactions of Pheo and QAin PSII core complexes fromA. marinausing Fourier transform infrared (FTIR) spectroscopy. Light-induced FTIR difference spectra upon single reduction of Pheo and QAshowed that spectral features in the regions of the keto and ester C=O stretches and the chlorin ring vibrations of Pheo and in the CO/CC stretching region of the QA−semiquinone anion inA. marinaare significantly different from those of the corresponding spectra in Chla-containing cyanobacteria. These observations indicate that the molecular interactions, including the hydrogen bond interactions at the C=O groups, of these cofactors are modified in their binding sites of PSII proteins. From these results, along with the sequence information of the D1 and D2 proteins, it is suggested thatA. marinatunes theEm’s of Pheo and QAby altering nearby hydrogen bond networks to modify the structures of the binding pockets of these cofactors.