Biomedical Research Centre, Sheffield Hallam University, Sheffield, UK.
Protoplasma. 2012 Jan;249(1):21-30. doi: 10.1007/s00709-011-0270-9. Epub 2011 Apr 3.
Despite mitochondria and chloroplasts having their own genome, 99% of mitochondrial proteins (Rehling et al., Nat Rev Mol Cell Biol 5:519-530, 2004) and more than 95% of chloroplast proteins (Soll, Curr Opin Plant Biol 5:529-535, 2002) are encoded by nuclear DNA, synthesised in the cytosol and imported post-translationally. Protein targeting to these organelles depends on cytosolic targeting factors, which bind to the precursor, and then interact with membrane receptors to deliver the precursor into a translocase. The molecular chaperones Hsp70 and Hsp90 have been widely implicated in protein targeting to mitochondria and chloroplasts, and receptors capable of recognising these chaperones have been identified at the surface of both these organelles (Schlegel et al., Mol Biol Evol 24:2763-2774, 2007). The role of these chaperone receptors is not fully understood, but they have been shown to increase the efficiency of protein targeting (Young et al., Cell 112:41-50, 2003; Qbadou et al., EMBO J 25:1836-1847, 2006). Whether these receptors contribute to the specificity of targeting is less clear. A class of chaperone receptors bearing tetratricopeptide repeat domains is able to specifically bind the highly conserved C terminus of Hsp70 and/or Hsp90. Interestingly, at least of one these chaperone receptors can be found on each organelle (Schlegel et al., Mol Biol Evol 24:2763-2774, 2007), which suggests a universal role in protein targeting for these chaperone receptors. This review will investigate the role that chaperone receptors play in targeting efficiency and specificity, as well as examining recent in silico approaches to find novel chaperone receptors.
尽管线粒体和叶绿体拥有自己的基因组，但 99%的线粒体蛋白（Rehling 等人，《自然评论分子细胞生物学》5:519-530，2004 年）和超过 95%的叶绿体蛋白（Soll，《当代植物生物学观点》5:529-535，2002 年）都是由核 DNA 编码的，在细胞质中合成，然后进行翻译后转运。这些细胞器中的蛋白质靶向依赖于细胞质靶向因子，这些因子与前体结合，然后与膜受体相互作用，将前体递送入转运体。分子伴侣 Hsp70 和 Hsp90 广泛参与蛋白质向线粒体和叶绿体的靶向，并且在这两种细胞器的表面已经鉴定出能够识别这些伴侣的受体（Schlegel 等人，《分子生物学与进化》24:2763-2774，2007 年）。这些伴侣受体的作用尚未完全了解，但已证明它们可以提高蛋白质靶向的效率（Young 等人，《细胞》112:41-50，2003 年；Qbadou 等人，《欧洲分子生物学组织杂志》25:1836-1847，2006 年）。这些受体是否有助于靶向的特异性尚不清楚。一类具有四肽重复结构域的伴侣受体能够特异性地结合 Hsp70 和/或 Hsp90 的高度保守 C 端。有趣的是，至少有一种这些伴侣受体可以在每个细胞器上找到（Schlegel 等人，《分子生物学与进化》24:2763-2774，2007 年），这表明这些伴侣受体在蛋白质靶向中具有普遍作用。这篇综述将探讨伴侣受体在靶向效率和特异性中的作用，并研究最近的计算方法来寻找新的伴侣受体。
