Microbial rhodopsins of Halorubrum species isolated from Ejinoor salt lake in Inner Mongolia of China
Microbial rhodopsins of Halorubrum species isolated from Ejinoor salt lake in Inner Mongolia of China
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内蒙古额济诺尔盐湖中分离的 Halorubrum 物种的微生物视紫红质
DOI：
10.1039/c5pp00161g
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发表时间：
2015
影响因子：
3.1
通讯作者：
Kunio Ihara and Tatsuo Iwasa
中科院分区：
文献类型：
--
作者：
Chaoluomeng;Gang Dai;Takashi Kikukawa;Kunio Ihara and Tatsuo Iwasa
微生物视紫红质是以视网膜分子为光敏中心的光敏蛋白质。微生物视紫红质因其结构简单、功能多样而成为结构生物学研究的理想模型系统。本研究从中国内蒙古额济纳旗盐湖中分离到一株嗜盐古菌，其基因组中含有3个微生物视紫红质型基因。16 S rRNA序列分析表明，该菌株属于Halorubrum属，命名为Halorubrum sp.ejinoor（He）。其微生物视紫红质型基因的翻译氨基酸序列表明，它们是古视紫红质（HeAR），盐视紫红质（HeHR）和感觉视紫红质II（HeSRII）的同源物。采用RT-PCR方法检测3种基因的mRNA表达，Real-Time RT-PCR方法检测3种基因的表达量。HeSR Ⅱ的mRNA量最少，HeAR和HeHR的mRNA量分别是HeSR Ⅱ的30倍和10倍。光致pH变化的结果表明，在膜囊泡的氦光驱动的质子泵和光驱动的氯离子泵的存在。闪光灯引起的吸光度变化表明HeAR和HeHR是光活性的，并进行自己的光循环。结果表明，三个视紫红质型基因在该菌株中均有表达，其中至少有两个基因HeAR和HeHR具有类似盐生盐杆菌BR和HR的光化学和生理活性。据我们所知，这是首次报道盐红菌的HR同源物的生理活性。
Microbial rhodopsins are photoactive proteins that use a retinal molecule as the photoactive center. Because of structural simplicity and functional diversity, microbial rhodopsins have been an excellent model system for structural biology. In this study, a halophilic archaea that has three microbial rhodopsin-type genes in its genome was isolated from Ejinoor salt lake in Inner Mongolia of China. A sequence of 16S rRNA showed that the strain belongs toHalorubrumgenus and namedHalorubrumsp.ejinoor(He). The translated amino acid sequences of its microbial rhodopsin-type genes suggest that they are homologs of archaerhodopsin (HeAR), halorhodopsin (HeHR) and sensory rhodopsin II (HeSRII). The mRNAs of three types of genes were detected by RT-PCR and their amounts were investigated by Real-Time RT-PCR. The amount of mRNA ofHeSRII was the smallest and the amounts of ofHeAR andHeHR were 30 times and 10 times greater than that ofHeSRII. The results of light-induced pH changes suggested the presence of a light-driven proton pump and a light-driven chloride ion pump in the membrane vesicles ofHe. Flash induced absorbance changes of theHemembrane fraction indicated thatHeAR andHeHR are photoactive and undergo their own photocycles. This study revealed that three microbial rhodopsin-type genes are all expressed in the strain and at least two of them,HeAR andHeHR, are photochemically and physiologically active like BR and HR ofHalobacterium salinarum, respectively. To our knowledge, this is the first report of physiological activity of HR-homolog ofHalorubrumspecies.