Membrane dynamic processes require Arf GTPase activation by guanine nucleotide exchange factors (GEFs) with a Sec7 domain. Cytohesin family Arf GEFs function in signaling and cell migration through Arf GTPase activation on the plasma membrane and endosomes. In this study, the structural organization of two cytohesins (Grp1 and ARNO) was investigated in solution by size exclusion-small angle X-ray scattering and negative stain-electron microscopy and on membranes by dynamic light scattering, hydrogen-deuterium exchange-mass spectrometry and guanosine diphosphate (GDP)/guanosine triphosphate (GTP) exchange assays. The results suggest that cytohesins form elongated dimers with a central coiled coil and membrane-binding pleckstrin-homology (PH) domains at opposite ends. The dimers display significant conformational heterogeneity, with a preference for compact to intermediate conformations. Phosphoinositide-dependent membrane recruitment is mediated by one PH domain at a time and alters the conformational dynamics to prime allosteric activation by Arf-GTP. A structural model for membrane targeting and allosteric activation of full-length cytohesin dimers is discussed.

中文翻译：

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溶液中和膜上同二聚体细胞粘附素家族Arf GTPase交换因子的结构组织和动力学。

膜动态过程需要具有Sec7域的鸟嘌呤核苷酸交换因子（GEF）激活Arf GTPase。细胞粘附素家族Arf GEFs通过质膜和内体上的Arf GTPase活化在信号传导和细胞迁移中起作用。在这项研究中，通过尺寸排阻-小角度X射线散射和负染色电子显微镜研究了溶液中两种细胞粘附素（Grp1和ARNO）的结构组织，以及动态光散射，氢-氘交换质谱法研究了膜上的两种细胞粘附素以及鸟苷二磷酸（GDP）/鸟苷三磷酸（GTP）交换分析。结果表明，细胞黏附素形成细长的二聚体，在中央的卷曲螺旋和相对端的膜结合性pleckstrin同源性（PH）域。二聚体显示出显着的构象异质性，偏爱紧凑到中间构象。磷酸肌醇依赖性膜募集一次由一个PH结构域介导，并改变构象动力学，以引发由Arf-GTP引发的变构活化。膜靶向和全长细胞粘附素二聚体的变构激活的结构模型进行了讨论。