SEQUENTIAL ACTION OF MITOCHONDRIAL CHAPERONES IN PROTEIN IMPORT INTO THE MATRIX
SEQUENTIAL ACTION OF MITOCHONDRIAL CHAPERONES IN PROTEIN IMPORT INTO THE MATRIX
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DOI：
10.1002/j.1460-2075.1991.tb04891.x
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发表时间：
1991-11-01
期刊：
影响因子：
11.4
通讯作者：
SCHATZ, G
中科院分区：
文献类型：
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作者：
MANNINGKRIEG, UC;SCHERER, PE;SCHATZ, G
进入线粒体的蛋白质的移位和折叠是由两个基质定位的伴侣蛋白Mhsp70和Hsp60介导的。为了研究这些伴侣蛋白是顺序作用还是平行作用，我们用免疫共沉淀法研究了它们与新进口的酵母线粒体前体蛋白的相互作用。所有前体都与mhsp70瞬时结合。从mhsp70释放需要ATP的水解，并且不会立即产生紧密折叠的蛋白质。例如，当进口的小鼠二氢叶酸还原酶(一种可溶性单体酶)从mhsp70释放出来后，折叠到抗蛋白酶的构象只在一段时间后发生，并且比释放要慢得多。在标准进口条件下，不能检测到DHFR与Hsp60之间的显著关联。同样，新进口的HSP60亚基是作为一种不完全折叠、未组装的中间体从mhsp70中释放出来的，它在低温下积累，并在较高温度下以ATP依赖的方式组装成Hsp60 14-mer。Mas2p(MAS编码的加工蛋白酶的较大亚基)首先与mhsp70结合，然后与Hsp60结合，然后才与其伙伴亚基Mas1p组装。我们认为，mhsp70依赖于ATP的释放不足以导致进口蛋白质的折叠，而Hsp60和Mas2p的组装需要与mhsp70和Hsp60顺序的、依赖于ATP的相互作用。
Translocation and folding of proteins imported into mitochondria are mediated by two matrix-localized chaperones, mhsp70 and hsp60. In order to investigate whether these chaperones act sequentially or in parallel, we studied their interaction with newly imported precursor proteins in isolated yeast mitochondria by co-immunoprecipitation. All precursors bound transiently to mhsp70. Release from mhsp70 required hydrolysis of ATP and did not immediately generate a tightly folded protein. For example, after imported mouse dihydrofolate reductase (a soluble monomeric enzyme) had been released from mhsp70, folding to a protease resistant conformation occurred only after a lag and was much slower than the release. Under standard import conditions, no significant association of DHFR with hsp60 could be detected. Similarly, newly imported hsp60 subunit was released from mhsp70 as an incompletely folded, unassembled intermediate which accumulated at low temperature and assembled to hsp60 14-mer at higher temperature in an ATP-dependent manner. Mas2p (the larger subunit of the MAS-encoded processing protease) first bound to mhsp70, then to hsp60, and only then assembled with its partner subunit, Mas1p. We propose that ATP-dependent release from mhsp70 is insufficient to cause folding of imported proteins and that assembly of hsp60 and Mas2p requires sequential, ATP-dependent interactions with mhsp70 and hsp60.