Multiple 40-kDa heat-shock protein chaperones function in Tom70-dependent mitochondrial import
Multiple 40-kDa heat-shock protein chaperones function in Tom70-dependent mitochondrial import
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DOI：
10.1091/mbc.e07-01-0088
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发表时间：
2007-09-01
影响因子：
3.3
通讯作者：
Young, Jason C.
中科院分区：
文献类型：
--
作者：
Bhangoo, Melanie K.;Tzankov, Stefan;Young, Jason C.
通过线粒体外膜（Tom）70受体的移位酶输入的线粒体前蛋白在靶向线粒体外膜之前与胞质伴侣复合。腺嘌呤核苷酸转运蛋白（ANT）遵循这一途径，其纯化的成熟形式与前蛋白相同。在网织红细胞裂解物中用分子伴侣重构纯化的ANT，并通过质谱法鉴定结合蛋白。除了70-kDa的热休克同源蛋白（Hsc 70）和90-kDa的热休克蛋白（Hsp 90），一个特定的辅助分子伴侣的子集被发现，但没有ESTA特异性的靶向factors. Interestingly，三个不同的热休克蛋白40相关的J-结构域蛋白被鉴定：DJA 1，DJA 2，和DJA 4。DjAs通过其C-末端区域以不同程度结合前蛋白。缺乏N-末端J-结构域的DJA显性阴性突变体损害线粒体输入。突变体阻断Hsc 70与前蛋白的结合，但效率不同。在Hsc 70 ATP酶的激活和Hsc 70依赖的蛋白质重折叠方面，DjAs也表现出显着的差异。在HeLa细胞中，DJAs增加了新的蛋白质折叠和线粒体输入，尽管程度不同。没有任何一个DJA在所有方面都比其他人优越上级，但每个人都有部分专业化的轮廓。热休克蛋白90辅伴侣p23和Aha 1也调节热休克蛋白90-前蛋白的相互作用。我们认为，多个cochaperones相似，但部分专业化的性能合作，在最佳的伴侣前蛋白复合物。
Mitochondrial preproteins that are imported via the translocase of the mitochondrial outer membrane (Tom)70 receptor are complexed with cytosolic chaperones before targeting to the mitochondrial outer membrane. The adenine nucleotide transporter (ANT) follows this pathway, and its purified mature form is identical to the preprotein. Purified ANT was reconstituted with chaperones in reticulocyte lysate, and bound proteins were identified by mass spectrometry. In addition to 70-kDa heat-shock cognate protein (Hsc70) and 90-kDa heat-shock protein (Hsp90), a specific subset of cochaperones were found, but no mitochondria-specific targeting factors were found. Interestingly, three different Hsp40-related J-domain proteins were identified: DJA1, DJA2, and DJA4. The DjAs bound preproteins to different extents through their C-terminal regions. DJA dominant-negative mutants lacking the N-terminal J-domains impaired mitochondrial import. The mutants blocked the binding of Hsc70 to preprotein, but with varying efficiency. The DjAs also showed significant differences in activation of the Hsc70 ATPase and Hsc70-dependent protein refolding. In HeLa cells, the DJAs increased new protein folding and mitochondrial import, although to different extents. No single DJA was superior to the others in all aspects, but each had a profile of partial specialization. The Hsp90 cochaperones p23 and Aha1 also regulated Hsp90-preprotein interactions. We suggest that multiple cochaperones with similar yet partially specialized properties cooperate in optimal chaperone-preprotein complexes.