Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Protein Sci. 2011 Jan;20(1):107-17. doi: 10.1002/pro.542.
p115-RhoGEF (p115) belongs to the family of RGS-containing guanine nucleotide exchange factors for Rho GTPases (RGS-RhoGEFs) that are activated by G12 class heterotrimeric G protein α subunits. All RGS-RhoGEFs possess tandemly linked Dbl-homology (DH) and plekstrin-homology (PH) domains, which bind and catalyze the exchange of GDP for GTP on RhoA. We have identified that the linker region connecting the N-terminal RGS-homology (RH) domain and the DH domain inhibits the intrinsic guanine nucleotide exchange (GEF) activity of p115, and determined the crystal structures of the DH/PH domains in the presence or absence of the inhibitory linker region. An N-terminal extension of the canonical DH domain (the GEF switch), which is critical to GEF activity, is well folded in the crystal structure of DH/PH alone, but becomes disordered in the presence of the linker region. The linker region is completely disordered in the crystal structure and partially disordered in the molecular envelope calculated from measurements of small angle x-ray scattering (SAXS). It is possible that Gα subunits activate p115 in part by relieving autoinhibition imposed by the linker region.
p115-RhoGEF（p115）属于包含 RGS 的 Rho GTP 酶鸟嘌呤核苷酸交换因子（RGS-RhoGEFs）家族，其被 G12 类异三聚体 G 蛋白α亚基激活。所有的 RGS-RhoGEFs 都具有串联的 Dbl 同源（DH）和 pleckstrin 同源（PH）结构域，可结合并催化 RhoA 上 GDP 向 GTP 的交换。我们已经确定，连接 N 端 RGS 同源（RH）结构域和 DH 结构域的连接区抑制了 p115 的固有鸟嘌呤核苷酸交换（GEF）活性，并确定了存在或不存在抑制性连接区时 DH/PH 结构域的晶体结构。对于 GEF 活性至关重要的经典 DH 结构域的 N 端延伸（GEF 开关）在单独的 DH/PH 晶体结构中折叠良好，但在连接区存在的情况下变得无序。连接区在晶体结构中完全无序，在从小角度 X 射线散射（SAXS）测量计算的分子包络中部分无序。Gα 亚基可能通过解除连接区施加的自动抑制来部分激活 p115。
