Characterization of a Cyanobacterial Chloride-pumping Rhodopsin and Its Conversion into a Proton Pump
Characterization of a Cyanobacterial Chloride-pumping Rhodopsin and Its Conversion into a Proton Pump
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DOI：
10.1074/jbc.m115.688614
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发表时间：
2016-01-01
影响因子：
4.8
通讯作者：
Demura, Makoto
中科院分区：
文献类型：
--
作者：
Hasemi, Takatoshi;Kikukawa, Takashi;Demura, Makoto
光驱动离子泵浦视紫红质广泛存在于微生物体内，目前分为外向型H+、Na+泵和内向型Cl-泵。这些不同的类型共享一个共同的蛋白质结构，并利用相同发色团的光异构化，视网膜，来引发光反应。尽管有这些相似之处，成功的泵-泵转换仅限于H+泵细菌视紫红质，它在1995年通过单一氨基酸替代被转换为氯-泵。在这项研究中，我们首次报道了从氯离子泵浦到氢离子泵浦的反向转换的成功。蓝藻中的一种新的微生物视紫红质(Mr HR)具有氯泵的功能，属于一个与已知的氯泵相去甚远的簇。通过单一的氨基酸替换，MR HR被转化为H+泵，在H+接力反应中几乎完全由可解离残基起作用。MR HR很可能是从一个H+泵进化而来的，但它还没有高度优化为一个成熟的氯-泵。
Light-driven ion-pumping rhodopsins are widely distributed in microorganisms and are now classified into the categories of outward H+ and Na+ pumps and an inward Cl- pump. These different types share a common protein architecture and utilize the photoisomerization of the same chromophore, retinal, to evoke photoreactions. Despite these similarities, successful pump-to-pump conversion had been confined to only the H+ pump bacteriorhodopsin, which was converted to a Cl- pump in 1995 by a single amino acid replacement. In this study we report the first success of the reverse conversion from a Cl- pump to a H+ pump. A novel microbial rhodopsin (MrHR) from the cyanobacterium Mastigocladopsis repens functions as a Cl- pump and belongs to a cluster that is far distant from the known Cl- pumps. With a single amino acid replacement, MrHR is converted to a H+ pump in which dissociable residues function almost completely in the H+ relay reactions. MrHR most likely evolved from a H+ pump, but it has not yet been highly optimized into a mature Cl- pump.