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首页> 外文期刊>Molecular and Cellular Biology >Protein Import Channel of the Outer Mitochondrial Membrane: a Highly Stable Tom40-Tom22 Core Structure Differentially Interacts with Preproteins, Small Tom Proteins, and Import Receptors
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Protein Import Channel of the Outer Mitochondrial Membrane: a Highly Stable Tom40-Tom22 Core Structure Differentially Interacts with Preproteins, Small Tom Proteins, and Import Receptors

机译：外部线粒体膜的蛋白质导入通道：高度稳定的Tom40-Tom22核心结构与前蛋白，小汤姆蛋白和导入受体差异相互作用。

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The preprotein translocase of the yeast mitochondrial outer membrane (TOM) consists of the initial import receptors Tom70 and Tom20 and a ～400-kDa (400 K) general import pore (GIP) complex that includes the central receptor Tom22, the channel Tom40, and the three small Tom proteins Tom7, Tom6, and Tom5. We report that the GIP complex is a highly stable complex with an unusual resistance to urea and alkaline pH. Under mild conditions for mitochondrial lysis, the receptor Tom20, but not Tom70, is quantitatively associated with the GIP complex, forming a 500K to 600K TOM complex. A preprotein, stably arrested in the GIP complex, is released by urea but not high salt, indicating that ionic interactions are not essential for keeping the preprotein in the GIP complex. Under more stringent detergent conditions, however, Tom20 and all three small Tom proteins are released, while the preprotein remains in the GIP complex. Moreover, purified outer membrane vesicles devoid of translocase components of the intermembrane space and inner membrane efficiently accumulate the preprotein in the GIP complex. Together, Tom40 and Tom22 thus represent the functional core unit that stably holds accumulated preproteins. The GIP complex isolated from outer membranes exhibits characteristic TOM channel activity with two coupled conductance states, each corresponding to the activity of purified Tom40, suggesting that the complex contains two simultaneously active and coupled channel pores.
机译：酵母线粒体外膜（TOM）的前蛋白转位酶由最初的进口受体Tom70和Tom20和一个〜400 kDa（400 K）的一般进口孔（GIP）复合体组成，其中包括中央受体Tom22，Tom40通道和三种小的Tom蛋白Tom7，Tom6和Tom5。我们报告说，GIP复合物是高度稳定的复合物，对尿素和碱性pH值具有非同寻常的抵抗力。在温和的线粒体裂解条件下，受体Tom20（而不是Tom70）与GIP复合物定量结合，形成500K至600K TOM复合物。稳定地滞留在GIP络合物中的预蛋白由尿素释放，但不释放高盐，这表明离子相互作用对于将预蛋白保留在GIP络合物中不是必需的。然而，在更严格的去污剂条件下，Tom20和所有三个小的Tom蛋白被释放，而前蛋白保留在GIP复合物中。此外，纯化的外膜囊泡没有膜间空间和内膜的跨酶组分，可有效地在GIP复合物中积聚前蛋白。因此，Tom40和Tom22共同代表了稳定保留积聚的前蛋白的功能核心单元。从外膜分离出的GIP复合物表现出特征性的TOM通道活性，具有两个耦合的电导状态，每个状态对应于纯化的Tom40的活性，表明该复合物包含两个同时激活和耦合的通道孔。

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