Ryan K R, Jensen R E
Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Biol Chem. 1993 Nov 15;268(32):23743-6.
Mas6p is an integral membrane protein of the yeast mitochondrial inner membrane, which is essential for mitochondrial protein import (1). To determine whether Mas6p is directly involved in recognizing precursors or translocating them across the inner membrane, we asked if Mas6p was in close proximity to precursor proteins being imported into mitochondria. We report here that Mas6p can be chemically cross-linked to an imported protein arrested in transit through the mitochondrial inner membrane. Antiserum to Mas6p specifically immunoprecipitates one of several different mitochondrial proteins that are cross-linked to blocked precursors. Our results strongly suggest that Mas6p physically interacts with precursors during their translocation into the matrix. In addition, at least two other mitochondrial proteins that are each cross-linked to arrested precursors can be coimmunoprecipitated along with Mas6p under non-denaturing conditions. These observations provide evidence for a complex of proteins including Mas6p, each of which interacts with mitochondrial precursors during import.
Mas6p是酵母线粒体内膜的一种整合膜蛋白，对于线粒体蛋白质的输入至关重要（1）。为了确定Mas6p是否直接参与识别前体蛋白或将它们转运穿过内膜，我们探究了Mas6p是否与正在被输入线粒体的前体蛋白紧密相邻。我们在此报告，Mas6p可以通过化学交联与一种在穿过线粒体内膜的转运过程中被阻滞的输入蛋白相结合。针对Mas6p的抗血清能特异性免疫沉淀与受阻前体蛋白发生交联的几种不同线粒体蛋白之一。我们的结果有力地表明，Mas6p在将前体蛋白转运到线粒体基质的过程中与其发生了物理相互作用。此外，在非变性条件下，至少还有另外两种与受阻前体蛋白发生交联的线粒体蛋白可以与Mas6p一起被共免疫沉淀。这些观察结果为包括Mas6p在内的一种蛋白质复合物提供了证据，其中每种蛋白质在蛋白质输入过程中都与线粒体前体蛋白相互作用。
