Pumping mechanism of NM-R3, a light-driven bacterial chloride importer in the rhodopsin family
Pumping mechanism of NM-R3, a light-driven bacterial chloride importer in the rhodopsin family
复制标题
DOI：
10.1126/sciadv.aay2042
复制
发表时间：
2020-02
期刊：
影响因子：
13.6
通讯作者：
J. Yun;M. Ohki;Jae-Hyun Park;N. Ishimoto;A. Sato‐Tomita;Wonbin Lee;Zeyu Jin;J. Tame;N. Shibayama;Sam-Yong Park;Weontae Lee
中科院分区：
文献类型：
--
作者：
J. Yun;M. Ohki;Jae-Hyun Park;N. Ishimoto;A. Sato‐Tomita;Wonbin Lee;Zeyu Jin;J. Tame;N. Shibayama;Sam-Yong Park;Weontae Lee
我们使用 95 至 140 K 的光激发晶体确定了氯泵 NM-R3 中的离子传导途径和蛋白质动力学。最近发现，来自海洋黄杆菌 Nonlabens marinus 的新鉴定的微生物视紫红质 NM-R3 可以驱动氯离子吸收，扩展了我们对生物能量转换机制多样性的理解。为了阐明其功能背后的机制，我们对不同强度和温度的激光脉冲产生的暗态和早期中间光激发态下的 NM-R3 晶体结构进行了表征。模型中五个不同位置的氯离子位移反映了详细的阴离子传导途径，并且通过突变测定和光谱法鉴定了与活性相关的关键残基 - Cys105、Ser60、Gln224 和 Phe90。与其他蛋白质（包括密切相关的向外钠离子泵）的比较揭示了关键基序，并为视紫红质 NQ 亚家族的光驱动离子跨膜运输提供了结构见解。出乎意料的是，NM-R3 中视网膜对光刺激的反应似乎与细菌视紫红质中的反应有很大不同。
We identify the ion conduction pathway and protein dynamics in chloride pump NM-R3 using photoexcited crystals at 95 to 140 K. A newly identified microbial rhodopsin, NM-R3, from the marine flavobacterium Nonlabens marinus, was recently shown to drive chloride ion uptake, extending our understanding of the diversity of mechanisms for biological energy conversion. To clarify the mechanism underlying its function, we characterized the crystal structures of NM-R3 in both the dark state and early intermediate photoexcited states produced by laser pulses of different intensities and temperatures. The displacement of chloride ions at five different locations in the model reflected the detailed anion-conduction pathway, and the activity-related key residues—Cys105, Ser60, Gln224, and Phe90—were identified by mutation assays and spectroscopy. Comparisons with other proteins, including a closely related outward sodium ion pump, revealed key motifs and provided structural insights into light-driven ion transport across membranes by the NQ subfamily of rhodopsins. Unexpectedly, the response of the retinal in NM-R3 to photostimulation appears to be substantially different from that seen in bacteriorhodopsin.