Demonstration of a Light-Driven SO42- Transporter and Its Spectroscopic Characteristics
Demonstration of a Light-Driven SO42- Transporter and Its Spectroscopic Characteristics
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DOI：
10.1021/jacs.6b12139
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发表时间：
2017-03-29
影响因子：
15
通讯作者：
Sudo, Yuki
中科院分区：
文献类型：
--
作者：
Niho, Akiko;Yoshizawa, Susumu;Sudo, Yuki
在生物体中，离子转运蛋白在跨细胞膜的离子梯度的产生和消散中起重要作用。微生物视紫红质利用太阳能选择性地运输同源离子，其中迄今为止鉴定的底物离子仅限于单价离子，如H+，Na+和Cl-。在这里，我们报告了一种新的视紫红质从蓝藻集胞藻属PCC 7509，向内传输多原子二价硫酸根离子，SO 42-，其光谱性质的变化，在非光解和光解状态。在光照下，细胞表达的新的视紫红质，命名为集胞藻halorhodopsin（SyHR），仅在Cl-或SO 42-的存在下，显示出碱化的培养基。通过加入质子载体增强了碱化信号，表明和SO 42-的向内运输，随后的二次向内H+跨膜运动。Cl-和SO_（42）-的吸收光谱分别从542 ~ 536 nm和542 ~ 556 nm移动，表明它们与SyHR结合，Cl-和SO_（42）-的亲和力分别为0.112和5.81 mM。然后，我们进行了时间分辨光谱测量范围从飞秒到毫秒的时间域来阐明的结构和结构变化的SyHR在光反应。基于这些结果，我们提出了一个光循环模型SyHR在不存在或存在的基板离子与他们的摄取和释放的时间。因此，我们证明SyHR作为第一个光驱动的多原子二价阴离子（SO 42-）转运蛋白，并报告其光谱特性。
In organisms, ion transporters play essential roles in the generation and dissipation of ion gradients across cell membranes. Microbial rhodopsins selectively transport cognate ions using solar energy, in which the substrate ions identified to date have been confined to monovalent ions such as H+, Na+ and Cl-. Here we report a novel rhodopsin from the cyanobacterium Synechocystis sp. PCC 7509, which inwardly transports a polyatomic divalent sulfate ion, SO42-, with changes of its spectroscopic properties in both unphotolyzed and photolyzed states. Upon illumination, cells expressing the novel rhodopsin, named Synechocystis halorhodopsin (SyHR), showed alkalization of the medium only in the presence of Cl- or SO42-. That alkalization signal was enhanced by addition of a protonophore, indicating an inward transport of and SO42- with a subsequent secondary inward H+ movement across the membrane. The anion binding to SyHR was suggested by absorption spectral shifts from 542 to 536 nm for Cl- and from 542 to 556 nm for SO42-, and the affinities of Cl- and SO42- were estimated as 0.112 and 5.81 rriM, respectively. We then performed time-resolved spectroscopic measurements ranging from femtosecond to millisecond time domains to elucidate the structure and structural changes of SyHR during the photoreaction. Based on the results, we propose a photocycle model for SyHR in the absence or presence of substrate ions with the timing of their uptake and release. Thus, we demonstrate SyHR as the first light-driven polyatomic divalent anion (SO42-) transporter and report its spectroscopic characteristics.