Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
Department of Synaptic Plasticity, Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany.
Proc Natl Acad Sci U S A. 2017 Oct 31;114(44):11691-11696. doi: 10.1073/pnas.1703422114. Epub 2017 Oct 16.
Na/H antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life and play an essential role in cellular ion homeostasis. The NhaA crystal structure of has become the paradigm for this class of secondary active transporters. However, structural data are only available at low pH, where NhaA is inactive. Here, we adapted hydrogen/deuterium-exchange mass spectrometry (HDX-MS) to analyze conformational changes in NhaA upon Li binding at physiological pH. Our analysis revealed a global conformational change in NhaA with two sets of movements around an immobile binding site. Based on these results, we propose a model for the ion translocation mechanism that explains previously controversial data for this antiporter. Furthermore, these findings contribute to our understanding of related human transporters that have been linked to various diseases.
钠氢反向转运蛋白是一类在所有生命领域中进化保守的膜蛋白，在细胞离子稳态中发挥着重要作用。的 NhaA 晶体结构已成为该类次级主动转运蛋白的典范。然而，结构数据仅在低 pH 值下可用，此时 NhaA 是无活性的。在这里，我们采用氘氢交换质谱（HDX-MS）分析在生理 pH 值下 Li 结合时 NhaA 的构象变化。我们的分析揭示了 NhaA 的全局构象变化，其中两组运动围绕着一个固定的结合位点。基于这些结果，我们提出了一个离子转运机制模型，该模型解释了该反向转运蛋白之前有争议的数据。此外，这些发现有助于我们理解与各种疾病相关的人类相关转运蛋白。
