National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Graduate School of the Chinese Academy of Sciences, Beijing 100049, China.
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Biochem Biophys Res Commun. 2014 Mar 28;446(1):380-6. doi: 10.1016/j.bbrc.2014.02.125. Epub 2014 Mar 5.
ADP-ribosylation factors (Arfs) play key roles in controlling membrane traffic and organelle structures. The activation of Arfs from GDP to GTP binding form is triggered by the guanine exchange factors (GEFs). There are six families of Arf-GEFs with a common guanine exchange catalytic domain (Sec7 domain) and various mechanisms of guanine exchange activity regulation. A loop region (loop>J motif) just following the helix J of Sec7 domain was found conserved and important for the catalytic activity regulation of Arf-GEFs. However, the molecular detail of the role the loop>J motif plays has been yet unclear. Here, we studied the catalytic domain of Sec7p, a yeast trans-Golgi network membrane localized Arf-GEFs, and found that the loop>J motif is indispensible for its GEF catalytic activity. Crystallographic, NMR spectrum and mutagenesis studies suggested that the loop>J motif with a key conserved residue Ile1010 modulates the fine conformation of Sec7 domain and thereby regulates its guanine exchange activity.
ADP-核糖基化因子 (Arfs) 在控制膜运输和细胞器结构方面发挥着关键作用。Arfs 从 GDP 结合形式到 GTP 结合形式的激活是由鸟嘌呤交换因子 (GEFs) 触发的。有六个家族的 Arf-GEFs 具有共同的鸟嘌呤交换催化结构域 (Sec7 结构域) 和各种调节鸟嘌呤交换活性的机制。在 Sec7 结构域的螺旋 J 之后发现了一个保守的环区 (loop>J 模体)，对于 Arf-GEFs 的催化活性调节非常重要。然而，loop>J 模体所扮演的分子细节作用仍不清楚。在这里，我们研究了 Sec7p 的催化结构域，Sec7p 是一种酵母高尔基网络膜定位的 Arf-GEFs，发现 loop>J 模体对于其 GEF 催化活性是不可或缺的。晶体学、NMR 谱和突变研究表明，loop>J 模体中的关键保守残基 Ile1010 调节 Sec7 结构域的精细构象，从而调节其鸟嘌呤交换活性。
