An analysis of mitochondrial transport mechanisms and physiological functions of mammalian molecular chaperone HSP60

原核伴侣蛋白已经被很好地表征，Xu等人已经展示了不对称GroEL-GroES-(ADP)_7伴侣蛋白复合物的晶体结构。相反，哺乳动物伴侣蛋白同源物（HSP60/10）的生化特性尚未完全了解。我们利用信号序列亲和柱层析分析了HSP60信号序列的结合蛋白，只鉴定出一个分子量为70kDa的蛋白。用抗HSP70抗体进行免疫印迹鉴定，该蛋白为HSP70。我们也在体内研究了HSP60进入线粒体的情况。HSP60 mRNA为。限水大鼠肾乳头增加3 ~ 5天。免疫印迹法在正常大鼠肾乳头细胞质和线粒体中均检测到HSP60。限水大鼠肾乳头细胞质中该蛋白含量降低，但乳头线粒体中该蛋白含量升高。这些结果表明，哺乳动物分子伴侣子HSP60在正常条件下同时位于细胞质和线粒体中，在严重条件下，胞质HSP60通过胞质HSP70导入线粒体。

Prokaryotic chaperonin has been well characterized, and the crystal structure of the asymmetric GroEL-GroES-(ADP)_7 chaperonin complex has been shown by Xu et al. On the contrary, biochemical properties of mammalian chaperonin homolog (HSP60/10) have not yet fully understood.We have analyzed binding protein to the signal sequence of HSP60 using signal sequence affinity column chromatography and identified only one protein with molecular mass of 70kDa. The protein was identified as HSP70 on immunoblotting using an antibody against HSP70.We have also investigated import of HSP60 into mitochondria in vivo. The mRNA of HSP60 was.increased in the papilla of water- restricted rat kidneys for 3 or 5 days. On immunoblotting analysis, HSP60 was detected both in cytoplasm and mitochondria of normal rat kidney papilla. Although the quantity of the protein was decreased in the cytoplasm of water-restricted rat kidney papilla, the protein was increased in the mitochondria of the papilla.These results suggested that mammalian molecular chaperon HSP60 is located both in the cytoplasm and mitochondria under normal conditions, and that cytoplasmic HSP60 is imported into mitochondria under severe conditions through cytoplasmic HSP70.