Rhodopsin-bestrophin fusion proteins from unicellular algae form gigantic pentameric ion channels
Rhodopsin-bestrophin fusion proteins from unicellular algae form gigantic pentameric ion channels
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DOI：
10.1038/s41594-022-00783-x
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发表时间：
2022-06-16
影响因子：
16.8
通讯作者：
Shalev-Benami，Moran
中科院分区：
文献类型：
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作者：
Rozenberg，Andrey;Kaczmarczyk，Igor;Shalev-Benami，Moran
许多生物体利用视紫质（含有视网膜发色团的感光蛋白）来感知光。在这里，我们报告了最佳视紫红质的发现、结构和生物物理特征，最佳视紫红质是一种来自海洋单细胞藻类的微生物视紫红质亚家族，其中八个跨膜螺旋的一个视紫红质结构域，或者更常见的是串联的两个这样的结构域，在C端融合到斑黄蛋白通道。对视紫红质-视紫红质-黄斑黄蛋白融合体的冷冻电镜分析表明，它形成了一个五聚体巨复合物（~700kDa），其中五个视紫红质假二聚体围绕中心通道。最佳视紫红质是亚稳态的，在不同的变体中会在红色和绿色吸收或绿色和 UVA 吸收形式之间进行光转换。视网膜发色团在独特的结合袋中，从全反式光异构化为 11-顺式。异源表达的最佳视紫红质表现为光调制阴离子通道。
Many organisms sense light using rhodopsins, photoreceptive proteins containing a retinal chromophore. Here we report the discovery, structure and biophysical characterization of bestrhodopsins, a microbial rhodopsin subfamily from marine unicellular algae, in which one rhodopsin domain of eight transmembrane helices or, more often, two such domains in tandem, are C-terminally fused to a bestrophin channel. Cryo-EM analysis of a rhodopsin-rhodopsin-bestrophin fusion revealed that it forms a pentameric megacomplex (~700 kDa) with five rhodopsin pseudodimers surrounding the channel in the center. Bestrhodopsins are metastable and undergo photoconversion between red- and green-absorbing or green- and UVA-absorbing forms in the different variants. The retinal chromophore, in a unique binding pocket, photoisomerizes from all-transto 11-cisform. Heterologously expressed bestrhodopsin behaves as a light-modulated anion channel.