MECHANISM OF GALPHA-13 REGULATED RHOGEF ACTIVITY OF P115RHOGEF

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 p115 RhoGEF（p115）代表G12类异源三聚体G蛋白和小GT3 Rho之间的直接连接。p115（102 kDa）是Ga-13（Ga 13，42 kDa）的负调节因子和下游效应因子。在其N-末端，p115具有RhoGEF-RGS（rgRGS）结构域，其作为GT3活化蛋白（GAP）对Ga 13起作用。与Ga 13的结合也刺激其对RhoA的鸟嘌呤核苷酸交换（GEF）活性。p115的GEF活性通过串联的DH和PH结构域进行，其通过150个残基的接头区域与N-末端rgRGS结构域分开。已经确定了rgRGS结构域与Ga 13的复合物和与RhoA复合的DH-PH结构域的晶体结构。我们建议，结合Ga 13 p115导致后者进行实质性的构象变化，可能域旋转在一个或多个铰链点。这种构象变化是刺激p115对RhoA的GEF活性所必需的。我们建议使用小角X射线散射来确定p115的分子包络，以及它与Ga 13的复合物。原子分辨率的结构模型可用于至少80%的结构域，包括p115，并已确定的Ga 13的结构。了解p115及其同源物的分子基础，由G蛋白调节，应该提供深入了解这一特定的调节途径，以及增加我们的基本理解的一般机制的信号由G蛋白。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. p115RhoGEF (p115) represents a direct link between the G12 class heterotrimeric G proteins and the small GTPase Rho. p115 (102 kDa) is both a negative regulator and a downstream effector for Galpha-13 (Ga13, 42 kDa). At its N-terminus, p115 possesses a RhoGEF-RGS (rgRGS) domain that functions as a GTPase activating protein (GAP) towards Ga13. Binding to Ga13 also stimulates its Guanine Nucleotide Exchange (GEF) activity towards RhoA. The GEF activity of p115 is carried out by the tandem DH and PH domains, which are separated from the N-terminal rgRGS domain by a 150 residue linker region. Crystal structures of the complex of the rgRGS domain with Ga13 and the DH-PH domains in complex with RhoA have been determined. We propose that the binding of Ga13 to p115 causes the latter to undergo substantial conformational changes, possibly domain rotation at one or more hinge points. Such conformational changes are required for stimulation of the GEF activity of p115 towards RhoA. We propose to use small angle X-ray scattering to determine the molecular envelope of p115, and that of its complex with Ga13. Atomic-resolution structural models are available for at least 80% of the structural domains that comprise p115, and a structure for the Ga13 has been determined. Understanding the molecular basis by which p115 and its homologs are regulated by G proteins should provide insight into this specific pathway for regulation as well as increase our fundamental understanding of general mechanisms of signaling by G proteins.