McKenna Michael J, Sim Sue Im, Ordureau Alban, Wei Lianjie, Harper J Wade, Shao Sichen, Park Eunyong
Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Science. 2020 Sep 25;369(6511). doi: 10.1126/science.abc5809.
Organelle identity depends on protein composition. How mistargeted proteins are selectively recognized and removed from organelles is incompletely understood. Here, we found that the orphan P5A-adenosine triphosphatase (ATPase) transporter ATP13A1 (Spf1 in yeast) directly interacted with the transmembrane segment (TM) of mitochondrial tail-anchored proteins. P5A-ATPase activity mediated the extraction of mistargeted proteins from the endoplasmic reticulum (ER). Cryo-electron microscopy structures of Spf1 revealed a large, membrane-accessible substrate-binding pocket that alternately faced the ER lumen and cytosol and an endogenous substrate resembling an α-helical TM. Our results indicate that the P5A-ATPase could dislocate misinserted hydrophobic helices flanked by short basic segments from the ER. TM dislocation by the P5A-ATPase establishes an additional class of P-type ATPase substrates and may correct mistakes in protein targeting or topogenesis.
细胞器的特性取决于蛋白质组成。错误定位的蛋白质如何被细胞器选择性识别并清除，目前尚未完全了解。在这里，我们发现孤儿P5A - 三磷酸腺苷酶（ATP酶）转运体ATP13A1（酵母中的Spf1）直接与线粒体尾锚定蛋白的跨膜片段（TM）相互作用。P5A - ATP酶活性介导了错误定位的蛋白质从内质网（ER）的提取。Spf1的冷冻电子显微镜结构揭示了一个大的、可接近膜的底物结合口袋，该口袋交替面向内质网腔和细胞质，以及一种类似于α - 螺旋TM的内源性底物。我们的结果表明，P5A - ATP酶可以将由短碱性片段侧翼的错误插入的疏水螺旋从内质网中移出。P5A - ATP酶介导的TM移位建立了另一类P型ATP酶底物，并可能纠正蛋白质靶向或拓扑发生中的错误。
