Becker Thomas, Hritz Jozef, Vogel Markus, Caliebe Alexander, Bukau Bernd, Soll Jürgen, Schleiff Enrico
Botanisches Institut, LMU München, 80638 Munich, Germany.
Mol Biol Cell. 2004 Nov;15(11):5130-44. doi: 10.1091/mbc.e04-05-0405. Epub 2004 Aug 18.
Translocation of proteins across membranes is essential for the biogenesis of each cell and is achieved by proteinaceous complexes. We analyzed the translocation complex of the intermembrane space from chloroplasts and identified a 12-kDa protein associated with the Toc machinery. Toc12 is an outer envelope protein exposing a soluble domain into the intermembrane space. Toc12 contains a J-domain and stimulates the ATPase activity of DnaK. The conformational stability and the ability to stimulate Hsp70 are dependent on a disulfide bridge within the loop region of the J-domain, suggesting a redox-regulated activation of the chaperone. Toc12 is associated with Toc64 and Tic22. Its J-domain recruits the Hsp70 of outer envelope membrane to the intermembrane space translocon and facilitates its interaction to the preprotein.
蛋白质跨膜转运对于每个细胞的生物合成至关重要，并且是由蛋白质复合物实现的。我们分析了叶绿体膜间隙的转运复合物，并鉴定出一种与Toc机制相关的12 kDa蛋白质。Toc12是一种外膜蛋白，其可溶性结构域暴露于膜间隙中。Toc12含有一个J结构域，并刺激DnaK的ATP酶活性。其构象稳定性和刺激Hsp70的能力取决于J结构域环区域内的二硫键，这表明伴侣蛋白的激活受氧化还原调节。Toc12与Toc64和Tic22相关。其J结构域将外膜的Hsp70募集到膜间隙转运体，并促进其与前体蛋白的相互作用。
