The specialized role of Hsp70 in protein import

描述（由申请人提供）：70 kDa热休克蛋白（Hsp70s），也被称为分子伴侣蛋白，除了在蛋白质折叠中的一般作用外，已经进化到在特定的生物过程中起作用。例如，主要的线粒体Hsp70 （mtHsp70）在穿过线粒体内膜的蛋白质输入中起着核心作用。由于绝大多数线粒体蛋白是在细胞质核糖体上合成的，因此，正如细胞膜转位酶（TIM）和基于mtHsp70的“进口马达”成分的本质所表明的那样，高效的蛋白质易位对线粒体的生物发生至关重要。Tim44是TIM复合物的外周膜组分，被认为是将mtHsp70连接到输入通道，并在结合底物蛋白（易位多肽）后将其从转位酶中释放出来。然而，人们对mtHsp70:Tim44相互作用以及mtHsp70:Tim44复合物在肽结合后不稳定的机制知之甚少。本提案的目的是更好地理解“进口马达”和TIM复合体的伴侣成分之间的相互作用及其在易位过程中的重要性。使用酿酒酵母作为模型系统，我的目的是剖析mtHsp70:Tim44相互作用，并测试这种相互作用对蛋白质易位的动态性质的重要性。我的实验结果将为这一重要的生物过程提供见解，并作为hsp70如何进化出特定调节蛋白的例子：蛋白质相互作用，使它们能够在特殊的生物过程中发挥作用，同时利用它们的基本生化特性：与短疏水氨基酸段相互作用。最近的基因组数据表明，重要运动成分的表达调控可能参与心脏肥厚和糖尿病的治疗。此外，线粒体的生物发生依赖于在细胞质中翻译的数百种蛋白质的蛋白质易位，它在一定程度上与许多疾病（如神经系统疾病、癌症和代谢疾病）以及衰老过程有关，这表明基本的细胞生物学问题集中在公共卫生问题上。

DESCRIPTION (provided by applicant): The 70 kDa Heat shock proteins (Hsp70s), also known as molecular chaperones, have evolved to function in specialized biological processes, in addition to the general role in protein folding. For example, the major mitochondrial Hsp70 (mtHsp70) plays a central role in protein import across the mitochondrial inner membrane. Since the vast majority of mitochondrial proteins are synthesized on cytosolic ribosomes, efficient protein translocation is critical for mitochondrial biogenesis, as indicated by the essential nature of components of the translocase of the inner membrane (TIM) and the mtHsp70 based "import motor". Tim44, a peripheral membrane component of the TIM complex, is believed to serve as a tether for mtHsp70 to the import channel and release it from the translocase upon binding a substrate protein, the translocating polypeptide. However, little is understood about the mtHsp70:Tim44 interaction and the mechanism behind the destabilization of the mtHsp70:Tim44 complex upon peptide binding. The goal of this proposal is to better understand the interaction between chaperone components of the "import motor" and the TIM complex and their importance in the translocation process. Using Saccharomyces cerevisiae as a model system, I aim to dissect the mtHsp70:Tim44 interaction and test the importance for the dynamic nature of this interaction on protein translocation. The results of my experiments will provide insight into this important biological process, as well as serve as an example of how Hsp70s have evolved specific regulated protein:protein interaction that allow them to function in specialized biological processes while utilizing their fundamental biochemical property: interaction with short hydrophobic segments of amino acids. Recent genomic data suggested that the regulation of expression of import motor components may be involved in heart hypertrophy treatments and diabetes. Moreover, mitochondria, whose biogenesis depends upon protein translocation of hundreds of proteins translated in the cytosol, are involved, in part, in numerous diseases (e.g. neurological disorders, cancer, and metabolic diseases), as well as the aging processes, indicating that the basic cell biological problems converge on the issues of public health.