STRUCTURE/FUNCTION OF UBIQUITIN CONJUGATING ENZYMES

泛素与蛋白质的翻译后连接被用于 真核生物靶向广泛的蛋白质进行选择性降解。 选择性地去除蛋白质是许多细胞 过程和泛素的要求已被证明为过程 从决定细胞在分裂，分化， 肿瘤发生和衰老到更具体的过程如DNA修复， 炎症反应、信号转导和异常信号的清除 proteins. 其中许多过程也在紧张的调查中 因为它们与人类疾病有关。 肿瘤发生和 炎症反应是两个例子。 蛋白质泛素化的特异性是由一个家族赋予的， 相关的蛋白质称为泛素结合酶（Ubc）。 成员 该家族与一组独特的底物结合蛋白相互作用 (also称为E3），正是Ubc和 E3蛋白使该途径能够靶向广泛的蛋白质， 降解 Ubc蛋白都有一个共同的保守结构域，大约150-170 个氨基酸残基 I类酶是最小的， 完全由这个领域组成。 这个保守的结构域在更大的， 多功能Ubc也可以自主运行。 因此，必须 独特的结构特征嵌入在一个保守的结构域， 使每种酶能够特异性相互作用单个Ubc蛋白 有自己的E3蛋白 Ubc序列的分析和三个 I类酶的已知晶体结构使我们配制了一种 预测UBC的相似性和差异的通用模型 在结构上表现出来。 我们的长期目标是确定 Ubc蛋白中的区域被用于其功能。 具体目标 本研究期间的主要任务是：1）分析突变对 选择的Ubc在酵母S.酿酒厂，目的是 定义负责Ubc与E3相互作用的区域， 2）启动确定Ubc 4-E3晶体结构的研究 复合物; 3）定义E3蛋白，其在Ubc 7依赖的 通路

The posttranslational attachment of ubiquitin to proteins is used in eukaryotes to target a broad range of proteins for selective degradation. Selective removal of proteins is required for a number of cellular processes and a requirement for ubiquitin has been shown for processes ranging from the determination of cell fate in division, differentiation, oncogenesis and senescence to more specific processes such as DNA repair, inflammatory response, signal transduction and the removal of abnormal proteins. Many of these processes are also under intense investigation because of their relevance in human diseases. Oncogenesis and the inflammatory responses are two examples. The specificity of protein ubiquitination is conferred by a family of related proteins known as ubiquitin conjugating-enzymes (Ubc). Members in this family interact with a distinct set of substrate-binding proteins (also known as E3), and it is these cascades of interaction between Ubc and E3 proteins that enable the pathway to target a broad range of proteins for degradation. Ubc proteins all share a common conserved domain of approximately 150-170 amino acid residues. The Class I enzymes are the smallest and are comprised entirely of this domain. This conserved domain in larger, multifunctional Ubc's can also function autonomously. Thus, there must be unique structural features embedded in the conserved domain of an individual Ubc protein that enable each enzyme to interact specifically with its own set of E3 proteins. Analyses of Ubc sequences and the three known crystal structures of Class I enzymes have led us to formulate a general model that predicts how similarity and differences in Ubc's are manifested structurally. Our long term goal is to determine how specific regions in Ubc proteins are utilized for its function. The specific aims for this research period is 1) to analyze the effect of mutations on the function of selected Ubc's in the yeast S. cerevisiae, with the intention of defining those regions that are responsible for Ubc interaction with E3, 2)to initiate studies toward determining the crystal structure of a Ubc4-E3 complex; 3) to define E3 proteins that function in the Ubc7-dependent pathway.