Cherfils J, Ménétrey J, Mathieu M, Le Bras G, Robineau S, Béraud-Dufour S, Antonny B, Chardin P
Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR 9063, Gif-sur-Yvette, France.
Nature. 1998 Mar 5;392(6671):101-5. doi: 10.1038/32210.
Small G proteins switch from a resting, GDP-bound state to an active, GTP-bound state. As spontaneous GDP release is slow, guanine-nucleotide-exchange factors (GEFs) are required to promote fast activation of small G proteins through replacement of GDP with GTP in vivo. Families of GEFs with no sequence similarity to other GEF families have now been assigned to most families of small G proteins. In the case of the small G protein Arf1, the exchange of bound GDP for GTP promotes the coating of secretory vesicles in Golgi traffic. An exchange factor for human Arf1, ARNO, and two closely related proteins, named cytohesin 1 and GPS1, have been identified. These three proteins are modular proteins with an amino-terminal coiled-coil, a central Sec7-like domain and a carboxy-terminal pleckstrin homology domain. The Sec7 domain contains the exchange-factor activity. It was first found in Sec7, a yeast protein involved in secretion, and is present in several other proteins, including the yeast exchange factors for Arf, Geal and Gea2. Here we report the crystal structure of the Sec7 domain of human ARNO at 2 A resolution and the identification of the site of interaction of ARNO with Arf.
小G蛋白从静止的、结合GDP的状态转变为活跃的、结合GTP的状态。由于GDP的自发释放很慢，因此在体内需要鸟嘌呤核苷酸交换因子（GEF）通过用GTP取代GDP来促进小G蛋白的快速激活。现在，与其他GEF家族没有序列相似性的GEF家族已被指定给大多数小G蛋白家族。就小G蛋白Arf1而言，结合的GDP与GTP的交换促进了高尔基体运输中分泌小泡的包被。已鉴定出人类Arf1的交换因子ARNO以及两种密切相关的蛋白质，即细胞粘着蛋白1和GPS1。这三种蛋白质是模块化蛋白质，具有氨基末端卷曲螺旋、中央Sec7样结构域和羧基末端普列克底物蛋白同源结构域。Sec7结构域具有交换因子活性。它最初在Sec7中被发现，Sec7是一种参与分泌的酵母蛋白，并且存在于其他几种蛋白质中，包括Arf、Geal和Gea2的酵母交换因子。在这里，我们报告了人类ARNO的Sec7结构域在2埃分辨率下的晶体结构以及ARNO与Arf相互作用位点的鉴定。
