Cyr D M, Stuart R A, Neupert W
Institut für Physiologische Chemie, Universität München, Germany.
J Biol Chem. 1993 Nov 15;268(32):23751-4.
The mitochondrial presequence initiates protein translocation across the inner membrane of mitochondria in a delta psi-dependent step. We have investigated the role of matrix ATP in this process. When matrix ATP was reduced to interfere with the function of mitochondrial heat shock protein 70, presequence translocation across the inner membrane was strongly inhibited. This was accompanied by the accumulation of an import intermediate that was unprocessed and accessible to protease added to the intact mitochondria. Both delta psi and matrix ATP were required for further translocation of this intermediate into the matrix. When ATP levels are insufficient to support protein import, it appears that the presequence becomes translocated across the inner membrane, but delta psi does not maintain it in the matrix. Presequence translocation across the inner membrane is thus a reversible reaction, and a step dependent on matrix ATP is required to make it unidirectional. Based on these observations, a model on the role of delta psi, mthsp70, and matrix ATP in presequence translocation across the inner membrane is presented.
线粒体前导序列在一个依赖于线粒体膜电位差（Δψ）的步骤中启动蛋白质穿过线粒体内膜的转运。我们研究了线粒体基质ATP在这一过程中的作用。当降低基质ATP以干扰线粒体热休克蛋白70的功能时，前导序列穿过内膜的转运受到强烈抑制。这伴随着一种未加工的导入中间体的积累，该中间体可被添加到完整线粒体中的蛋白酶所作用。这种中间体进一步转运到基质中既需要线粒体膜电位差也需要基质ATP。当ATP水平不足以支持蛋白质导入时，前导序列似乎穿过了内膜，但线粒体膜电位差并未将其维持在基质中。因此，前导序列穿过内膜的转运是一个可逆反应，并且需要一个依赖于基质ATP的步骤使其变为单向。基于这些观察结果，我们提出了一个关于线粒体膜电位差、线粒体热休克蛋白70和基质ATP在前导序列穿过内膜转运中作用的模型。
