Department of Molecular Biology and Genetics, Aarhus University, Denmark; The Danish Research Institute for Translational Neuroscience (DANDRITE), Nordic EMBL Partnership for Molecular Medicine, Denmark.
Department of Molecular Biology and Genetics, Aarhus University, Denmark; The Danish Research Institute for Translational Neuroscience (DANDRITE), Nordic EMBL Partnership for Molecular Medicine, Denmark; Aarhus Institute of Advanced Studies (AIAS), Denmark; The Danish National Research Foundation Center for Proteins in Memory (PROMEMO), Denmark.
J Mol Biol. 2021 Aug 6;433(16):167015. doi: 10.1016/j.jmb.2021.167015. Epub 2021 Apr 30.
Many bacteria export intracellular calcium using active transporters homologous to the sarco/endoplasmic reticulum Ca-ATPase (SERCA). Here we present three crystal structures of Ca-ATPase 1 from Listeria monocytogenes (LMCA1). Structures with BeF mimicking a phosphoenzyme state reveal a closed state, which is intermediate between the outward-open E2P and the proton-occluded E2-P* conformations known for SERCA. It suggests that LMCA1 in the E2P state is pre-organized for dephosphorylation upon Ca release, consistent with the rapid dephosphorylation observed in single-molecule studies. An arginine side-chain occupies the position equivalent to calcium binding site I in SERCA, leaving a single Ca binding site in LMCA1, corresponding to SERCA site II. Observing no putative transport pathways dedicated to protons, we infer a direct proton counter transport through the Ca exchange pathways. The LMCA1 structures provide insight into the evolutionary divergence and conserved features of this important class of ion transporters.
许多细菌使用与肌浆/内质网 Ca-ATP 酶（SERCA）同源的主动转运体将细胞内的钙输出。在这里，我们展示了来自李斯特菌（LMCA1）的 Ca-ATP 酶 1 的三个晶体结构。具有 BeF 模拟磷酸化酶状态的结构揭示了一种封闭状态，该状态处于外向开放的 E2P 和 SERCA 已知的质子封闭 E2-P*构象之间的中间状态。这表明，在 Ca 释放时，LMCA1 处于 E2P 状态，预先组织好进行去磷酸化，这与在单分子研究中观察到的快速去磷酸化一致。一个精氨酸侧链占据与 SERCA 中钙结合位点 I 等效的位置，使 LMCA1 中只剩下一个 Ca 结合位点，对应于 SERCA 位点 II。没有观察到专门用于质子的假定运输途径，我们推断质子通过 Ca 交换途径进行直接反向运输。LMCA1 结构为研究这一重要的离子转运蛋白家族的进化分歧和保守特征提供了深入的了解。
