Yu Zhiheng, Gonciarz Malgorzata D, Sundquist Wesley I, Hill Christopher P, Jensen Grant J
Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
J Mol Biol. 2008 Mar 21;377(2):364-77. doi: 10.1016/j.jmb.2008.01.009. Epub 2008 Jan 12.
The type I AAA (ATPase associated with a variety of cellular activities) ATPase Vps4 and its co-factor Vta1p/LIP5 function in membrane remodeling events that accompany cytokinesis, multivesicular body biogenesis, and retrovirus budding, apparently by driving disassembly and recycling of membrane-associated ESCRT (endosomal sorting complex required for transport)-III complexes. Here, we present electron cryomicroscopy reconstructions of dodecameric yeast Vps4p complexes with and without their microtubule interacting and transport (MIT) N-terminal domains and Vta1p co-factors. The ATPase domains of Vps4p form a bowl-like structure composed of stacked hexameric rings. The two rings adopt dramatically different conformations, with the "upper" ring forming an open assembly that defines the sides of the bowl and the lower ring forming a closed assembly that forms the bottom of the bowl. The N-terminal MIT domains of the upper ring localize on the symmetry axis above the cavity of the bowl, and the binding of six extended Vta1p monomers causes additional density to appear both above and below the bowl. The structures suggest models in which Vps4p MIT and Vta1p domains engage ESCRT-III substrates above the bowl and help transfer them into the bowl to be pumped through the center of the dodecameric assembly.
I型AAA（与多种细胞活动相关的ATP酶）ATP酶Vps4及其辅助因子Vta1p/LIP5在伴随胞质分裂、多囊泡体生物发生和逆转录病毒出芽的膜重塑事件中发挥作用，显然是通过驱动膜相关转运所需内体分选复合物（ESCRT）-III复合物的拆卸和循环利用来实现的。在此，我们展示了含有和不含微管相互作用与转运（MIT）N端结构域及Vta1p辅助因子的十二聚体酵母Vps4p复合物的冷冻电镜重建结构。Vps4p的ATP酶结构域形成一个由堆叠的六聚体环组成的碗状结构。这两个环呈现出截然不同的构象，“上”环形成一个开放组装体，界定了碗的侧面，而下环形成一个封闭组装体，构成了碗的底部。上环的N端MIT结构域位于碗腔上方的对称轴上，六个延伸的Vta1p单体的结合导致在碗的上方和下方均出现额外的密度。这些结构提示了一些模型，其中Vps4p的MIT和Vta1p结构域在碗上方与ESCRT-III底物结合，并帮助将它们转移到碗中，以便通过十二聚体组装体的中心进行泵送。
