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首页> 外文期刊>Molecular and Cellular Biology >Role of heat shock cognate 70 protein in import of ornithine transcarbamylase precursor into mammalian mitochondria.
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Role of heat shock cognate 70 protein in import of ornithine transcarbamylase precursor into mammalian mitochondria.

机译：热休克同源70蛋白在鸟氨酸转氨甲酰酶前体输入哺乳动物线粒体中的作用。

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The roles of the 70-kDa cytosolic heat shock protein (hsp70) in import of precursor proteins into the mitochondria were postulated to be related to (i) unfolding of precursor proteins in the cytosol, (ii) maintenance of the import-competent state, and (iii) unfolding and transport of precursor proteins through contact sites, in cooperation with matrix hsp70. We examined roles of cytosolic hsp70 family members in import of ornithine transcarbamylase precursor (pOTC) into rat liver mitochondria, using an in vitro import system and antibodies against hsp70. Immunoblot analysis using an hsc70 (70-kDa heat shock cognate protein)-specific monoclonal antibody and a polyclonal antibody that reacts with both hsc70 and hsp70 showed that hsc70 is the only or major form of hsp70 family members in the rabbit reticulocyte lysate. The hsc70 antibody did not inhibit pOTC import when added prior to import assay. However, when pOTC was synthesized in the presence of the antibody and then subjected to import assay, pOTC import was markedly decreased. pOTC import was also decreased when the precursor was synthesized in the lysate depleted for hsc70 by treatment with hsc70 antibody-conjugated Sepharose. This reduction was almost completely restored by readdition of purified mouse hsc70 during pOTC synthesis. The readdition of hsc70 after pOTC synthesis and only during the import assay was not effective. Thus, once import competence of pOTC was lost, hsc70 was ineffective for restoration. Newly synthesized pOTC lost import competence in the absence of hsc70 somewhat more rapidly than in its presence. These results indicate that hsc70 is required during pOTC synthesis and not during import into the mitochondria. hsc70 presumably binds to pOTC polypeptide and maintains it in an import-competent form.
机译：推测70-kDa胞质热休克蛋白（hsp70）在将前体蛋白导入线粒体中的作用与（i）前体蛋白在胞质溶胶中解折叠，（ii）保持导入能力状态， （iii）与基质hsp70合作，通过接触位点展开和转运前体蛋白。我们使用体外导入系统和针对hsp70的抗体，研究了胞质hsp70家族成员在鸟氨酸转氨甲酰酶前体（pOTC）导入大鼠肝线粒体中的作用。使用hsc70（70 kDa热休克同源蛋白）特异性单克隆抗体和与hsc70和hsp70均反应的多克隆抗体进行的免疫印迹分析表明，hsc70是兔网织红细胞裂解物中hsp70家族成员的唯一或主要形式。在导入分析之前添加hsc70抗体不会抑制pOTC导入。然而，当在抗体存在下合成pOTC然后进行导入分析时，pOTC导入显着减少。当通过hsc70抗体偶联的琼脂糖凝胶处理在hsc70耗尽的裂解物中合成前体时，pOTC的导入也减少了。在pOTC合成过程中，通过纯化小鼠hsc70的重新分配，这种还原几乎完全得以恢复。在pOTC合成后且仅在导入检测过程中对hsc70的读取无效。因此，一旦失去了pOTC的进口能力，hsc70就无法恢复。在缺少hsc70的情况下，新合成的pOTC失去了进口能力，比在其存在下更快。这些结果表明，在pOTC合成过程中需要hsc70，而在导入线粒体过程中则不需要。 hsc70可能与pOTC多肽结合，并将其保持在具有导入能力的形式。

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