Structural Basis of Sarco/Endoplasmic Reticulum Ca2+-ATPase 2b Regulation via Transmembrane Helix Interplay
Structural Basis of Sarco/Endoplasmic Reticulum Ca2+-ATPase 2b Regulation via Transmembrane Helix Interplay
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DOI：
10.1016/j.celrep.2019.03.106
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发表时间：
2019-04-23
期刊：
影响因子：
8.8
通讯作者：
Inaba, Kenji
中科院分区：
文献类型：
--
作者：
Inoue, Michio;Sakuta, Nanami;Inaba, Kenji
肌浆/内质网 (ER) Ca2+-ATPase 2b (SERCA2b) 是一种普遍表达的膜蛋白，可促进 Ca2+ 从细胞质摄取到 ER。 SERCA2b 包括一个特征性的第 11 跨膜螺旋 (TM11)，后跟一个腔尾，但这些 C 端片段调节 SERCA 的结构基础仍不清楚。在这里，我们确定了 SERCA2b 及其 C 端剪接变体 SERCA2a 的晶体结构，两者均处于 E1-2Ca(2+)-腺苷酸 1 亚甲基二磷酸酯 (AMPPCP) 状态。尽管与之前报道的 SERCA2b 结构模型存在差异，但发现 TM11 位于 TM10 附近，并与 L8/9 环的一部分和 TM10 的 N 末端相互作用较弱，从而抑制 SERCA2b 催化循环。因此，TM11 与其邻近残基之间相互作用的突变破坏导致 SERCA2b 显示出类似 SERCA2a 的 ATP 酶活性。我们认为 TM11 通过微调与其他跨膜区域的分子内相互作用，作为 SERCA2b 活性的关键调节剂。
Sarco/endoplasmic reticulum (ER) Ca2+-ATPase 2b (SERCA2b) is a ubiquitously expressed membrane protein that facilitates Ca2+ uptake from the cytosol to the ER. SERCA2b includes a characteristic 11th transmembrane helix (TM11) followed by a luminal tail, but the structural basis of SERCA regulation by these C-terminal segments remains unclear. Here, we determined the crystal structures of SERCA2b and its C-terminal splicing variant SERCA2a, both in the E1-2Ca(2+)-adenyly1 methylenediphosphonate (AMPPCP) state. Despite discrepancies with the previously reported structural model of SERCA2b, TM11 was found to be located adjacent to TM10 and to interact weakly with a part of the L8/9 loop and the N-terminal end of TM10, thereby inhibiting the SERCA2b catalytic cycle. Accordingly, mutational disruption of the interactions between TM11 and its neighboring residues caused SERCA2b to display SERCA2a-like ATPase activity. We propose that TM11 serves as a key modulator of SERCA2b activity by fine-tuning the intramolecular interactions with other transmembrane regions.