Centre for Medical Biotechnology, Faculty of Biology, University of Duisburg-Essen, 45117 Essen, Germany.
Centre for Medical Biotechnology, Faculty of Biology, University of Duisburg-Essen, 45117 Essen, Germany; Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
Mol Cell. 2018 Nov 15;72(4):766-777.e6. doi: 10.1016/j.molcel.2018.09.020. Epub 2018 Oct 18.
The functional diversity of protein phosphatase-1 (PP1), with its countless substrates, relies on the ordered assembly of alternative PP1 holoenzymes. Here, we show that newly synthesized PP1 is first held by its partners SDS22 and inhibitor-3 (I3) in an inactive complex, which needs to be disassembled by the p97 AAA-ATPase to promote exchange to substrate specifiers. Unlike p97-mediated degradative processes that require the Ufd1-Npl4 ubiquitin adapters, p97 is targeted to PP1 by p37 and related adapter proteins. Reconstitution with purified components revealed direct interaction of the p37 SEP domain with I3 without the need for ubiquitination, and ATP-driven pulling of I3 into the central channel of the p97 hexamer, which triggers dissociation of I3 and SDS22. Thus, we establish regulatory ubiquitin-independent protein complex disassembly as part of the functional arsenal of p97 and define an unanticipated essential step in PP1 biogenesis that illustrates the molecular challenges of ordered subunit exchange.
蛋白磷酸酶-1（PP1）的功能多样性依赖于其无数的底物，这依赖于替代的 PP1 全酶的有序组装。在这里，我们表明，新合成的 PP1 首先被其伴侣 SDS22 和抑制剂-3（I3）结合在一个无活性的复合物中，该复合物需要 p97 AAA-ATP 酶的解组装来促进与底物特异性蛋白的交换。与需要 Ufd1-Npl4 泛素连接酶的 p97 介导的降解过程不同，p97 是由 p37 和相关衔接蛋白靶向 PP1 的。用纯化的成分进行重建揭示了 p37 SEP 结构域与 I3 的直接相互作用，而不需要泛素化，并且 ATP 驱动的 I3 拉入 p97 六聚体的中央通道，这触发了 I3 和 SDS22 的解离。因此，我们将调节性非依赖泛素的蛋白质复合物解组装确立为 p97 功能武器库的一部分，并定义了 PP1 生物发生中的一个意料之外的基本步骤，说明了有序亚基交换的分子挑战。
