Szollosi Andras, Vieira-Pires Ricardo S, Teixeira-Duarte Celso M, Rocha Rita, Morais-Cabral João H
IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
PLoS Biol. 2016 Jan 15;14(1):e1002356. doi: 10.1371/journal.pbio.1002356. eCollection 2016 Jan.
KtrAB belongs to the Trk/Ktr/HKT superfamily of monovalent cation (K+ and Na+) transport proteins that closely resemble K+ channels. These proteins underlie a plethora of cellular functions that are crucial for environmental adaptation in plants, fungi, archaea, and bacteria. The activation mechanism of the Trk/Ktr/HKT proteins remains unknown. It has been shown that ATP stimulates the activity of KtrAB while ADP does not. Here, we present X-ray structural information on the KtrAB complex with bound ADP. A comparison with the KtrAB-ATP structure reveals conformational changes in the ring and in the membrane protein. In combination with a biochemical and functional analysis, we uncover how ligand-dependent changes in the KtrA ring are propagated to the KtrB membrane protein and conclude that, despite their structural similarity, the activation mechanism of KtrAB is markedly different from the activation mechanism of K+ channels.
KtrAB属于单价阳离子（K⁺和Na⁺）转运蛋白的Trk/Ktr/HKT超家族，与K⁺通道极为相似。这些蛋白质是众多细胞功能的基础，对植物、真菌、古细菌和细菌的环境适应性至关重要。Trk/Ktr/HKT蛋白质的激活机制尚不清楚。研究表明，ATP可刺激KtrAB的活性，而ADP则无此作用。在此，我们展示了与结合ADP的KtrAB复合物的X射线结构信息。与KtrAB-ATP结构的比较揭示了环和膜蛋白的构象变化。结合生化和功能分析，我们揭示了KtrA环中依赖配体的变化是如何传递到KtrB膜蛋白的，并得出结论，尽管KtrAB与K⁺通道在结构上相似，但其激活机制与K⁺通道的激活机制明显不同。
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