Toc64--a preprotein-receptor at the outer membrane with bipartide function.
Toc64--a preprotein-receptor at the outer membrane with bipartide function.
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DOI：
10.1016/j.jmb.2007.01.047
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发表时间：
2007-04
影响因子：
5.6
通讯作者：
Soumya Qbadou;T. Becker;T. Bionda;Katharina Reger;Maike Ruprecht;J. Soll;E. Schleiff
中科院分区：
文献类型：
--
作者：
Soumya Qbadou;T. Becker;T. Bionda;Katharina Reger;Maike Ruprecht;J. Soll;E. Schleiff
蛋白质跨膜易位是由前体蛋白靶向的膜中存在的易位机制辅助的。易位子亚基可以在功能上分为受体蛋白，保证了这台机器的特异性和易位通道。在叶绿体的外包膜上，有两组受体蛋白调节蛋白的转运，它们面向细胞质或作用于膜间隙。首先，Toc64是叶绿体外包膜转座子（Toc复合体）的受体，具有双重功能。Toc64通过含有三个四肽重复基序的细胞质暴露结构域识别Hsp90传递的前体蛋白，并且如本文所示，Toc64还作为面向膜间空间的复合体的主要组分。后者由定位于膜间空间的Hsp70、其相互作用伙伴Toc12、含j结构域的蛋白和膜间空间蛋白Tic22组成。我们分析了Toc64的膜间空间结构域。该结构域参与前蛋白识别并与toc复合物结合，独立于Toc64受体的胞质结构域。因此，Toc64参与了在膜的两个位点外包膜的前蛋白易位。
Protein translocation across membranes is assisted by translocation machineries present in the membrane targeted by the precursor proteins. Translocon subunits can be functionally divided into receptor proteins warranting the specificity of this machine and a translocation channel. At the outer envelope of chloroplasts two sets of receptor proteins regulate protein translocation facing the cytosol or acting in the intermembrane space. One, Toc64 is a receptor of the translocon at the outer envelope of chloroplasts (Toc complex) with dual function. Toc64 recognizes Hsp90 delivered precursor proteins via a cytosolic exposed domain containing three tetratrico-peptide repeat motifs and as demonstrated in here, Toc64 functions also as a major component of a complex facing the intermembrane space. The latter complex is composed of an Hsp70 localized in the intermembrane space, its interaction partner Toc12, a J-domain containing protein and the intermembrane space protein Tic22. We analyzed the intermembrane space domain of Toc64. This domain is involved in preprotein recognition and association with the Toc-complex independent of the cytosolic domain of the Toc64 receptor. Therefore, Toc64 is involved in preprotein translocation across the outer envelope at both sites of the membrane.