Biochemical and Spectroscopic Characterizations of a Hybrid Light-Harvesting Reaction Center Core Complex
Biochemical and Spectroscopic Characterizations of a Hybrid Light-Harvesting Reaction Center Core Complex
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DOI：
10.1021/acs.biochem.8b00644
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发表时间：
2018-07-31
期刊：
影响因子：
2.9
通讯作者：
Wang-Otomo, Zheng-Yu
中科院分区：
文献类型：
--
作者：
Kimura, Yukihiro;Hashimoto, Kanako;Wang-Otomo, Zheng-Yu
来自Thermochromatium tepidum的捕光1反应中心（LH 1-RC）复合物在915 nm处表现出由于Ca 2+的结合而导致的大幅度红移的LH 1 Q（y）吸收，导致从LH 1到反应中心（RC）的“上坡”能量转移。在最近的一项研究中，我们开发了一个异源表达系统（菌株TS 2），以构建一个功能性杂交LH 1-RC与LH 1从Tch。tepidum和Rhodobacter sphaeroides [Nagashima，K.副总统，等人（2017）Proc. Natl. Acad. Sci.美国114，10906]。在这里，我们提出了详细的表征的混合LH 1-RC从菌株TS 2。金属离子对TS 2菌株光合生长的影响表明，Ca 2+是其生长所必需的元素，Tch也是如此。Tepidum，而不是Rba。sphaeroides TS 2 LH 1-RC的热稳定性强烈依赖于Ca 2+的方式类似于天然Tch。Tepidum，但在菌株TS 2中，异源LH 1与RC之间的相互作用相对较弱。傅里叶变换红外分析表明，TS 2 LH 1的钙结合位点是相似的，但不完全相同的Tch。单调乏味。稳态和时间分辨荧光测量表明，从LH 1到RC的上坡能量转移速率与能隙Rba的数量级有关。sphaeroides，Tch. tepidum和菌株TS 2;然而，LH 1荧光的量子产率没有表现出这样的相关性。在此基础上，我们讨论了Ca ~（2+）的作用，LH 1与不同物种RC之间的相互作用，以及上坡能量传递机制。
The light-harvesting 1 reaction center (LH1-RC) complex from Thermochromatium tepidum exhibits a largely red-shifted LH1 Q(y) absorption at 915 nm due to binding of Ca2+, resulting in an "uphill" energy transfer from LH1 to the reaction center (RC). In a recent study, we developed a heterologous expression system (strain TS2) to construct a functional hybrid LH1-RC with LH1 from Tch. tepidum and the RC from Rhodobacter sphaeroides [Nagashima, K. V. P., et al. (2017) Proc. Natl. Acad. Sci. U.S. A. 114, 10906]. Here, we present detailed characterizations of the hybrid LH1-RC from strain TS2. Effects of metal cations on the phototrophic growth of strain TS2 revealed that Ca2+ is an indispensable element for its growth, which is also true for Tch. tepidum but not for Rba. sphaeroides. The thermal stability of the TS2 LH1-RC was strongly dependent on Ca2+ in a manner similar to that of the native Tch. tepidum, but interactions between the heterologous LH1 and RC became relatively weaker in strain TS2. A Fourier transform infrared analysis demonstrated that the Ca2+-binding site of TS2 LH1 was similar but not identical to that of Tch. tepidum. Steady-state and time-resolved fluorescence measurements revealed that the uphill energy transfer rate from LH1 to the RC was related to the energy gap in an order of Rba. sphaeroides, Tch. tepidum, and strain TS2; however, the quantum yields of LH1 fluorescence did not exhibit such a correlation. On the basis of these findings, we discuss the roles of Ca2+, interactions between LH1 and the RC from different species, and the uphill energy transfer mechanisms.