STRUCTURE/FUNCTION OF MITOTARGETING SIGNAL SEQUENCES

描述：线粒体基质空间蛋白由核基因编码。 并在合成后移位到细胞器中。一个N端子 多肽的延伸，称为前序，允许前体蛋白 为了识别线粒体并将其穿过两层膜 一个依赖能源的过程。导入后，通过以下方式删除前置序列 大多数前体蛋白，但不是所有前体蛋白都有蛋白分解作用。没有 线粒体前序列之间的同源氨基酸序列可以是 显示了它们的靶向特性。几乎没有什么 现有的定义序列或结构的实验数据 对加工现场的要求。主要的相似之处在于 线粒体前序列是一个净正电荷，预测的 形成两亲性结构的能力。它之前一直是 用二维核磁共振、圆二色谱和荧光光谱进行了测定 技术，与线粒体相对应的合成肽 前序列由两亲的阿尔法螺旋组成。初步数据显示， 前序列与线粒体膜结合的能力和 N端的螺旋稳定性是线粒体的重要特征 瞄准目标。此外，还开发了一个模型，用于满足以下要求 正在处理。该模型采用主要和次要相结合的方式 作为加工识别基元的前序列的结构 蛋白酶。对结构要求的进一步理解 与线粒体结合的预测序，移位到基质中，并成为 通过对它们进行突变，就可以获得经过该酶处理的蛋白质。 含有蛋白质的进口速率和线粒体结合特性 将测量突变的前序列。突变预测序的成功 在执行这些功能时将与生物物理数据进行比较 关于相关合成肽的结构和膜结合。 我们的目标是确定螺旋度、电荷和 疏水性使各种装订的进口和加工 前置序列。为了进一步实现这一目标，将在 转化酵母菌和HeLa细胞以验证基于In 体外研究与体内进口研究一致。因此，彻底 蛋白质知识是针对线粒体的，以及如何防止 将获得蛋白质进口。这一知识可以用来确定 线粒体的治疗剂。一种这样的战略可能涉及 通常由线粒体基因编码的蛋白质的进口，当 这个基因已经被破坏了。对进口有透彻的理解，它可能会 使恢复线粒体功能成为可能，使患有 线粒体编码蛋白的遗传缺陷。此外，它是 可以想象，有机类似物可以被设计成拮抗剂和 防止输入到线粒体。

DESCRIPTION: Mitochondrial matrix space proteins are coded by nuclear genes and translocated into the organelle after their synthesis. An N-terminal extension of polypeptide, called a presequence, allows the precursor protein to recognize mitochondria and be trannnslocated across the two membranes in an energy-dependent process. After import, the presequence is removed by proteolysis for most, but not all precursor proteins. There is no homologous amino acid sequence among mitochondrial presequences that can be shown to give rise to their targeting properties. There is little experimental data available that defines the sequence or structural requirements for the processing site. The major similarities in mitochondrial presequences are a net positive charge and the predicted capability to form amphiphilic structures. It has previously been determined, using two dimensional NMR, circular dichroism and fluorescence techniques, that synthetic peptides corresponding to mitochondrial presequences form amphiphilic alpha helices. Preliminary data suggests that the ability of the presequence to bind to the mitochondrial membrane and the helical stability at the N-terminus are crucial features of mitochondrial targeting. In addition, a model has been developed for the requirements of processing. The model employs a combination of the primary and secondary structure of presequences as a recognition motif for the processing protease. Further understanding of the structural requirements for presequences to bind to mitochondria, be translocated into the matrix and be processed by the protease will be gained by making mutations in them. Import rates and mitochondrial binding properties of proteins containing the mutated presequences will be measured. The success of a mutant presequence in carrying out these functions will be compared to biophysical data regarding structure and membrane binding of the related synthetic peptide. The goal is to determine the contribution that helicity, charge and hydrophobicity make to the binding import and processing of various presequences. To further realize this goal, import will be performed in transformed yeast and HeLa cells to verify that the conclusions based on in vitro studies are consistent with import in vivo. As a result, thorough knowledge of proteins are targeted to mitochondria and how to prevent protein import will be obtained. This knowledge could be used to target theraputic agents to mitochondria. One such strategy could involve the import of a protein that is normally encoded by a mitochondrial gene, when that gene has been damaged. With a thorough understanding of import, it may become possible to restore mitochondrial function to people afflicted by genetic defects in mitochondria-encoded proteins. In addition, it is conceivable that organic analogs could be designed to act as antagonists and prevent import into mitochondria.