PROTEIN TARGETING TO THE INNER MITOCHONDRIAL MEMBRANE

线粒体内膜由进入内膜的多肽组成。 从基质和细胞质(即膜间空间)表面。 那些从基质侧进入膜的多肽是 由线粒体基因编码，翻译到核糖体上，结合到 内膜的基质面，并插入膜中 共同翻译。那些进入细胞质表面的多肽 由核基因编码，由可溶性核糖体翻译(或者，在某些情况下 例，核糖体结合到线粒体膜)，并插入 翻译后进入细胞膜。这两类膜蛋白 必须正确定位到内膜，然后定位到 它们所在的寡聚蛋白质复合体。在这项研究中，我们 建议确定起作用的分子决定因素 将每一类具有代表性的酵母多肽分类为一种蛋白质 内膜内的低聚物。我们将使用酵母细胞色素C氧化酶 线粒体基因产物亚基II和酵母细胞色素C氧化酶 V亚基是一种核基因产物，是具有代表性的多肽。为 亚基V，我们计划通过定向突变和基因内突变来鉴定 回复分析，多肽及其“前导”中的结构域 肽“是其功能插入到体内所必需的 薄膜。我们还计划通过对基因外的分析来确定 反转体，指定辅助蛋白(可溶性和膜)的基因 这是将其插入内膜所必需的。对子单位而言 第二，我们计划分析其“先导肽”的功能，并通过 回复分析，确定其蛋白质产物与其相互作用的基因 “先导肽。”最后，我们希望确定是否插入这些 可以发生两种蛋白质进入内膜的相对两侧 同时。 这项研究将增进我们对膜蛋白生物发生的理解 一般而言，线粒体内膜的生物发生，以及 尤其是细胞呼吸的重要组成部分。

The mitochondrial inner membrane is composed of polypeptides which enter it from both matrix and cytoplasmic (i.e. intermembrane space) surfaces. Those polypeptides which enter the membrane from the matrix side are encoded by mitochondrial genes, translated on ribosomes which are bound to the matrix face of the inner membrane, and inserted into the membrane co-translationally. Those polypeptides which enter the cytoplasmic face are encoded by nuclear genes, translated by soluble ribosomes (or, in some cases, ribosomes bound to the outer mitochondrial membrane), and inserted into the membrane post-translationally. Both classes of membrane proteins must be correctly targeted to the inner membrane and then localized to the oligomeric protein complex within which they reside. In this study we propose to identify the molecular determinants which operate to target and sort one representative yeast polypeptide of each class to a protein oligomer within the inner membrane. We will use yeast cytochrome c oxidase subunit II, a mitochondrial gene product, and yeast cytochrome c oxidase subunit V, a nuclear gene product, as the representative polypeptides. For subunit V, we plan to identify, by directed mutagenesis and intragenic revertant analysis, those domains within the polypeptide and its "leader peptide" which are required for its functional insertion into the inner membrane. We also plan to identify, by the analysis of extragenic revertants, genes which specify ancillary proteins (soluble and membrane) that are required for its insertion into the inner membrane. For subunit II, we plan to analyze the function of its "leader peptide" and, through revertant analysis, identify genes whose protein products interact with its "leader peptide." Finally, we hope to determine if the insertion of these two proteins into opposite sides of the inner membrane can occur simultaneously. This study should enhance our understanding of membrane protein biogenesis in general and the biogenesis of the inner mitochondrial membrane, an essential component of cellular respiration, in particular.