Specificities for the small G proteins ARF1 and ARF6 of the guanine nucleotide exchange factors ARNO and EFA6
Specificities for the small G proteins ARF1 and ARF6 of the guanine nucleotide exchange factors ARNO and EFA6
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DOI：
10.1074/jbc.m103284200
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发表时间：
2001-07-06
影响因子：
4.8
通讯作者：
Franco, M
中科院分区：
文献类型：
--
作者：
Macia, E;Chabre, M;Franco, M
ARF 1和ARF 6是ADP核糖基化因子（ARF）小G蛋白亚家族的远缘成员。它们独特的细胞功能必须由与不同效应物和调节物相互作用的特异性引起，包括鸟嘌呤核苷酸交换因子（GEF）、ARF核苷酸结合位点开放剂（ARNO）和EFA 6是类似的ARF-GEF，两者都包含催化“Sec 7”结构域和普列克底物蛋白同源结构域。在体内，ARNO，像ARF 1一样，主要是细胞溶质，在高尔基体和质膜上有少量的定位; EFA 6，像ARF 6一样，局限于质膜。然而，根据不同的条件，ARNO似乎活跃的ARF 6以及ARF 1，在这里，我们分析这些ARF-GEF选择性的起源。在体外，在磷脂膜存在下，ARNO优先激活ARF 1，而ARF 6轻微激活，而EFA 6仅激活ARF 6，EFA 6对ARF 6的刺激效率与ARNO对ARF 1的刺激效率相当，这些选择性由GEFs的Sec 7结构域单独决定，没有pleckstrin同源性和N-末端结构域，以及由ARF核心结构域决定，没有豆蔻酰化的N-末端螺旋;当在开关区域内不同的少数氨基酸在ARF 1和ARF 6之间置换时，它们不被修饰。因此，对ARF 1或ARF 6的选择性必须取决于与Sec 7结构域相互作用的ARF开关区域之间的细微折叠差异。
ARF1 and ARF6 are distant members of the ADP-ribosylation factor (ARF) small G-protein subfamily. Their distinct cellular functions must result from specificity of interaction with different effecters and regulators, including guanine nucleotide exchange factors (GEFs), ARF nucleotide-binding site opener (ARNO), and EFA6 are analogous ARF-GEFs, both comprising a catalytic "Sec7" domain and a pleckstrin homology domain. In vivo ARNO, like ARF1, is mostly cytosolic, with minor localizations at the Golgi and plasma membrane; EFA6, like ARF6, is restricted to the plasma membrane. However, depending on conditions, ARNO appears active on ARF6 as well as on ARF1, Here we analyze the origin of these ARF-GEF selectivities. In vitro, in the presence of phospholipid membranes, ARNO activates ARF1 preferentially and ARF6 slightly, whereas EFA6 activates ARF6 exclusively; the stimulation efficiency of EFA6 on ARF6 is comparable with that of ARNO on ARF1, These selectivities are determined by the GEFs Sec7 domains alone, without the pleckstrin homology and N-terminal domains, and by the ARF core domains, without the myristoylated N-terminal helix; they are not modified upon permutation between ARF1 and ARF6 of the few amino acids that differ within the switch regions. Thus selectivity for ARF1 or ARF6 must depend on subtle folding differences between the ARFs switch regions that interact with the Sec7 domains.