LEADER PEPTIDES--SUBUNITS OF MEMBRANE PROTEIN OLIGOMERS

许多完整的膜蛋白在原位是杂寡体。他们的 生物发生需要不同的亚基多肽靶向 正确的细胞内膜及其正确组装成功能 很复杂。此前的研究强调了氨基末端的重要性 将蛋白质定位于膜表面的“先导肽” 并随后将其插入膜中。他们还制作了 明确了插入或通过膜的蛋白质 共同翻译使用他们的“先导-肽”，与可溶性 蛋白质，来调节自己的翻译。尽管很明显 “前导肽”的重要性，它们的命运，在被 已处理的情况不确定。同样不确定的是，他们是否表现出其他 膜生物发生中的功能。 我们建议检验一个新的假说：“先导肽”的功能是 一些膜蛋白低聚体中的亚基。这个假说已经产生了。 最近测序的三个核编码多肽的发现 酵母细胞色素c氧化酶的亚基(vii、viia和viii)是同源的。 从其他无关的、核编码的已知“前导肽” 线粒体蛋白质。我们计划1)克隆和测序结构性的 这三个亚基的基因决定它们是否真的是“领导者” 来自更大的多肽前体的多肽，这些多肽前体从其 -COOH末端；2)通过在它们的 结构基因，如果它们是组装或发挥功能所必需的 全细胞色素C氧化酶；以及3)识别它们与之结合的蛋白质 如果我们发现它们是“先导肽”，那就是连续的。这些研究可能 识别膜生物发生和膜生物发生中的另一种作用 提供了关于装配的机制的重要线索 同一膜上的蛋白质低聚体的路径是协调的。

Many integral membrane proteins are hetero-oligomers in situ. Their biogenesis requires the targeting of different subunit polypeptides to the correct intracellular membrane and their proper assembly into a functional complex. Previous studies have stressed the importance of NH2-terminal "leader peptides" for both the targeting of proteins to membrane surfaces and their subsequent insertion into the membrane. They have also made clear that proteins which are inserted into or through membranes co-translationally use their "leader-peptides", in conjunction with soluble proteins, to regulate their own translation. Despite the obvious importance of "leader peptide" presequences, their fate, after being processed is uncertain. Also uncertain is whether they perform other functions in membrane biogenesis. We propose to test a new hypothesis: that "leader peptides" function as subunits in some membrane protein oligomers. This hypothesis has grown out of the finding that three recently sequenced nuclear-coded polypeptide subunits (VII, VIIa, and VIII) of yeast cytochrome c oxidase are homologous to known "leader peptides" from other, unrelated, nuclear-coded mitochondrial proteins. We plan to 1) clone and sequence the structural genes for these three subunits to determine if they are, in fact, "leader peptides" derived from larger polypeptide precursors extending from their -COOH terminus; 2) determine, by constructing null mutants in their structural genes, if they are required for the assembly or function of holocytochrome c oxidase; and 3) identify proteins with which they are contiguous should we find that they are "leader pepdides". The studies may identify another role for "leader peptides" in membrane biogenesis and provide an important clue regarding the mechanisms by which the assembly pathways of protein oligomers in the same membrane are coordinated.