Amor J C, Harrison D H, Kahn R A, Ringe D
Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Nature. 1994 Dec 15;372(6507):704-8. doi: 10.1038/372704a0.
ADP-ribosylation factors (ARFs) are essential and ubiquitous in eukaryotes, being involved in vesicular transport and functioning as an activator of phospholipase D (refs 1, 2) and cholera toxin. The functions of ARF proteins in membrane traffic and organelle integrity are intimately tied to its reversible association with membranes and specific interactions with membrane phospholipids. One common feature of these functions is their regulation by the binding and hydrolysis of GTP. Here we report the three-dimensional structure of full-length human ARF1 (M(r) 21,000) in its GDP-bound non-myristoylated form. The presence of a unique amino-terminal alpha-helix and loop, together with differences in Mg2+ ligation and the existence of a non-crystallographic dimer, set this structure apart from other GTP-binding proteins. These features provide a structural basis for the GTP-dependent modulation of membrane affinity, the lack of intrinsic GTPase activity, and the nature of effector binding surfaces.
ADP核糖基化因子（ARFs）在真核生物中是必需且普遍存在的，参与囊泡运输，并作为磷脂酶D（参考文献1、2）和霍乱毒素的激活剂发挥作用。ARF蛋白在膜运输和细胞器完整性方面的功能与其与膜的可逆结合以及与膜磷脂的特异性相互作用密切相关。这些功能的一个共同特征是它们受GTP结合和水解的调节。在此，我们报道了全长人ARF1（分子量21,000）处于结合GDP的非肉豆蔻酰化形式时的三维结构。独特的氨基末端α螺旋和环的存在，以及Mg2+配位的差异和非晶体学二聚体的存在，使该结构有别于其他GTP结合蛋白。这些特征为膜亲和力的GTP依赖性调节、缺乏内在GTP酶活性以及效应物结合表面的性质提供了结构基础。
