Nucleotides and Substrates Trigger the Dynamics of the Toc34 GTPase Homodimer Involved in Chloroplast Preprotein Translocation
Nucleotides and Substrates Trigger the Dynamics of the Toc34 GTPase Homodimer Involved in Chloroplast Preprotein Translocation
复制标题
DOI：
10.1016/j.str.2014.02.004
复制
发表时间：
2014-04-08
期刊：
影响因子：
5.7
通讯作者：
Schleiff, Enrico
中科院分区：
文献类型：
--
作者：
Lumme, Christina;Altan-Martin, Hasret;Schleiff, Enrico
GTP酶是控制许多关键细胞过程的分子开关。与真正的GTP酶不同，GAD-GTP酶是由核苷酸依赖的二聚体激活的，而GAD-GTP酶的研究较少。该家族的一个成员是参与调节前蛋白输入的叶绿体Toc34外膜转位酶。Toc34的GTPase循环被认为是易位调节的主要回路。与预期相反，以前的研究只产生了二聚体Toc34的边缘结构变化，以响应不同的核苷酸负载。参考PELDOR和FRET单分子和整体实验，我们描述了二聚体灵活性从紧密的GDP-到灵活的GTP负载状态的依赖核苷酸的转变。底物结合诱导GDP负载的二聚体打开。因此，由GTP水解引起的真正的GTP酶的结构动力学被底物依赖的二聚体灵活性所取代，这可能代表了GTP酶二聚的一般调控模式。
GTPases are molecular switches that control numerous crucial cellular processes. Unlike bona fide GTPases, which are regulated by intramolecular structural transitions, the less well studied GAD-GTPases are activated by nucleotide-dependent dimerization. A member of this family is the translocase of the outer envelope membrane of chloroplast Toc34 involved in regulation of preprotein import. The GTPase cycle of Toc34 is considered a major circuit of translocation regulation. Contrary to expectations, previous studies yielded only marginal structural changes of dimeric Toc34 in response to different nucleotide loads. Referencing PELDOR and FRET single-molecule and bulk experiments, we describe a nucleotide-dependent transition of the dimer flexibility from a tight GDP- to a flexible GTP-loaded state. Substrate binding induces an opening of the GDP-loaded dimer. Thus, the structural dynamics of bona fide GTPases induced by GTP hydrolysis is replaced by substrate-dependent dimer flexibility, which likely represents a general regulatory mode for dimerizing GTPases.