INHIBITOR OF APOPTOSIS PROTEINS: DOMAIN ORGANIZATION AND CONFORMATIONAL REARRANG

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 细胞凋亡抑制因子（Inhibitors of apoptosis，IAP）是一种能够抑制细胞凋亡的抗凋亡因子。 IAP家族成员除了赋予IAP蛋白E3泛素连接酶活性的C-末端RING结构域之外，还含有可变数量的蛋白质-蛋白质相互作用结构域。 小分子拮抗剂与细胞IAP（cIAP）内的选择性杆状病毒IAP重复（BIR）的结合促进cIAP自动泛素化和随后的蛋白酶体降解，从而释放cIAP对细胞凋亡的抑制。这种结合事件反过来影响E3连接酶活性的远程RING结构域内的手段仍然不清楚。 一个简单的假设是，拮抗剂结合导致cIAP蛋白经历从“封闭”到“开放”构象的结构重排，然后能够形成活性RING-RING二聚体。 在“闭合”状态下，该二聚体界面不可接近，并且不能形成活性二聚体。 在支持这一假设，我们发现，除了拮抗剂纯化，cIAP 1单体导致二聚体形成，天然凝胶电泳，尺寸排阻色谱和动态光散射测量监测。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Inhibitors of apoptosis (IAPs) are anti-apoptotic factors that block cell death in response to a variety of stimuli. IAP family members contain a variable number of protein-protein interaction domains in addition to a C-terminal RING domain that confers E3 ubiquitin ligase activity to the IAP proteins. Binding of small molecule antagonists to select baculovirus IAP repeats (BIR) within cellular IAPs (cIAPs) promotes cIAP auto-ubiquitination and subsequent proteasomal degradation, thereby releasing cIAP inhibition of apoptosis. The means by which this binding event in turn influences E3 ligase activity within the distant RING domain remains unclear. One simple hypothesis is that antagonist binding causes the cIAP protein to undergo a structural rearrangement from a "closed" to an "open" conformation, which is then competent to form active RING-RING dimers. In the "closed" state this dimer interface is inaccessible and active dimers cannot form. In support of this hypothesis, we find that addition of antagonist to purified, cIAP1 monomers causes dimer formation, as monitored by native gel electrophoresis, size exclusion chromatography and dynamic light scattering measurements.