Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, Germany.
Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
FEBS J. 2016 Apr;283(7):1232-8. doi: 10.1111/febs.13585. Epub 2015 Nov 26.
A key and common process present in organisms from all domains of life is the maintenance of the ion gradient between the inside and the outside of the cell. The gradient is generated by various active transporters, among which are the light-driven ion pumps of the microbial rhodopsin family. Whereas the proton-pumping and anion-pumping rhodopsins have been known for a long time, the cation (sodium) pumps were described only recently. Following the discovery, high-resolution atomic structures of the pump KR2 were determined that revealed the complete ion translocation pathway, including the positions of the characteristic Asn-Asp-Gln (NDQ) triad, the unusual ion uptake cavity acting as a selectivity filter, the unique N-terminal α-helix, capping the ion release cavity, and unexpected flexibility of the retinal-binding pocket. The structures also revealed pentamerization of KR2 and binding of sodium ions at the interface. Finally, on the basis of the structures, potassium-pumping KR2 variants have been designed, making the findings even more important for optogenetic applications. In this Structural Snapshot, we analyse the implications of the structural findings for understanding the sodium translocation mechanism and application of the pump and its mutants in optogenetics.
所有生命领域的生物中都存在一个关键且共同的过程，即维持细胞内外离子梯度。该梯度由各种主动转运蛋白产生，其中包括微生物视紫红质家族的光驱动离子泵。质子泵和阴离子泵视紫红质已经为人所知很长时间了，阳离子（钠）泵直到最近才被描述。在发现之后，确定了泵 KR2 的高分辨率原子结构，该结构揭示了完整的离子转运途径，包括特征性 Asn-Asp-Gln (NDQ) 三联体的位置、作为选择性过滤器的不寻常离子摄取腔、独特的 N 端α-螺旋、覆盖离子释放腔，以及出人意料的视黄醛结合口袋的灵活性。这些结构还揭示了 KR2 的五聚化和钠离子在界面处的结合。最后，基于这些结构，设计了钾泵 KR2 的变体，这使得这些发现对于理解钠转运机制以及该泵及其突变体在光遗传学中的应用更为重要。在这个结构快照中，我们分析了结构发现对理解钠转运机制以及该泵及其突变体在光遗传学中的应用的影响。
