Nishimura Taishi, Uno Chihiro, Ido Kunio, Nagao Ryo, Noguchi Takumi, Sato Fumihiko, Ifuku Kentaro
Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Graduate School of Science, Nagoya University, Aichi 464-8602, Japan.
Biochim Biophys Acta. 2014 Sep;1837(9):1447-53. doi: 10.1016/j.bbabio.2013.12.012. Epub 2014 Jan 2.
The PsbP protein is an extrinsic subunit of photosystem II (PSII) that is essential for photoautotrophic growth in higher plants. Several crystal structures of PsbP have been reported, but the binding topology of PsbP in PSII has not yet been clarified. In this study, we report that the basic pocket of PsbP, which consists of conserved Arg48, Lys143, and Lys160, is important for the electrostatic interaction with the PSII complex. Our release-reconstitution experiment showed that the binding affinities of PsbP-R48A, -K143A, and -K160A mutated proteins to PSII were lower than that of PsbP-WT, and triple mutations of these residues greatly diminished the binding affinity to PSII. Even when maximum possible binding had occurred, the R48A, K143A, and K160A proteins showed a reduced ability to restore the rate of oxygen evolution at low chloride concentrations. Fourier transform infrared resonance (FTIR) difference spectroscopy results were consistent with the above finding, and suggested that these mutated proteins were not able to induce the normal conformational change around the Mn cluster during S1 to S2 transition. Finally, chemical cross-linking experiments suggested that the interaction between the N-terminus of PsbP with PsbE was inhibited by these mutations. These data suggest that the basic pocket of PsbP is important for proper association and interaction with PSII. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
PsbP蛋白是光系统II（PSII）的一种外在亚基，对高等植物的光合自养生长至关重要。已有多篇关于PsbP晶体结构的报道，但PsbP在PSII中的结合拓扑结构尚未明确。在本研究中，我们报道了由保守的Arg48、Lys143和Lys160组成的PsbP碱性口袋，对与PSII复合物的静电相互作用很重要。我们的释放-重组实验表明，PsbP-R48A、-K143A和-K160A突变蛋白与PSII的结合亲和力低于野生型PsbP，这些残基的三重突变大大降低了与PSII的结合亲和力。即使发生了最大可能的结合，R48A、K143A和K160A蛋白在低氯浓度下恢复氧气释放速率的能力也有所降低。傅里叶变换红外共振（FTIR）差光谱结果与上述发现一致，表明这些突变蛋白在S1到S2转变过程中无法诱导锰簇周围的正常构象变化。最后，化学交联实验表明，这些突变抑制了PsbP N端与PsbE之间的相互作用。这些数据表明，PsbP的碱性口袋对于与PSII的正确缔合和相互作用很重要。本文是名为：光合作用促进可持续发展研究：生产清洁能源的关键的特刊的一部分。
