The human DnaJ homologue dj2 facilitates mitochondrial protein import and luciferase refolding.
The human DnaJ homologue dj2 facilitates mitochondrial protein import and luciferase refolding.
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DOI：
10.1083/jcb.139.5.1089
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发表时间：
1997-12-01
期刊：
影响因子：
--
通讯作者：
Mori M
中科院分区：
文献类型：
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作者：
Terada K;Kanazawa M;Bukau B;Mori M
DnaJ同源物与hsp70家族成员共同参与多种细胞过程，包括细胞内蛋白质运输和折叠。已经鉴定出存在于细胞质中的三种人类DnaJ同源物：dj1 (hsp40/hdj-1), dj2 （HSDJ/hdj-2）和神经元组织特异性hsj1。dj1被认为参与新生多肽的折叠，而其他DnaJ同源物的功能仍有待阐明。为了研究dj2和dj1的作用，我们开发了一种从兔网织细胞裂解物中去除和读取伴侣蛋白的系统。利用该系统，我们发现热休克同源70蛋白（hsc70）和dj2，而不是dj1，参与了预鸟氨酸转氨基甲酰基酶的线粒体进口。细菌DnaJ可以替代哺乳动物dj2在线粒体蛋白输入中的作用。我们还测试了这些DnaJ同源物对胍变性萤火虫荧光素酶折叠的影响。出乎意料的是，dj2，而不是dj1，与hsc70一起有效地重新折叠了蛋白质。我们认为dj2是哺乳动物细胞质中hsc70的功能伙伴DnaJ同源物。细菌DnaJ蛋白可以代替哺乳动物dj2蛋白进行荧光素酶的再折叠。因此，用于线粒体蛋白导入和蛋白折叠的细胞质伴侣系统是高度保守的，包括细菌中的DnaK和DnaJ，酵母中的Ssa1-4p和Ydj1p，哺乳动物中的hsc70和dj2。
DnaJ homologues function in cooperation with hsp70 family members in various cellular processes including intracellular protein trafficking and folding. Three human DnaJ homologues present in the cytosol have been identified: dj1 (hsp40/hdj-1), dj2 (HSDJ/hdj-2), and neuronal tissue-specific hsj1. dj1 is thought to be engaged in folding of nascent polypeptides, whereas functions of the other DnaJ homologues remain to be elucidated. To investigate roles of dj2 and dj1, we developed a system of chaperone depletion from and readdition to rabbit reticulocyte lysates. Using this system, we found that heat shock cognate 70 protein (hsc70) and dj2, but not dj1, are involved in mitochondrial import of preornithine transcarbamylase. Bacterial DnaJ could replace mammalian dj2 in mitochondrial protein import. We also tested the effects of these DnaJ homologues on folding of guanidine-denatured firefly luciferase. Unexpectedly, dj2, but not dj1, together with hsc70 refolded the protein efficiently. We propose that dj2 is the functional partner DnaJ homologue of hsc70 in the mammalian cytosol. Bacterial DnaJ protein could replace mammalian dj2 in the refolding of luciferase. Thus, the cytosolic chaperone system for mitochondrial protein import and for protein folding is highly conserved, involving DnaK and DnaJ in bacteria, Ssa1–4p and Ydj1p in yeast, and hsc70 and dj2 in mammals.