Moczko M, Schönfisch B, Voos W, Pfanner N, Rassow J
Biochemisches Institut Universität Freiburg, Germany.
J Mol Biol. 1995 Dec 8;254(4):538-43. doi: 10.1006/jmbi.1995.0636.
The mitochondrial heat shock protein Hsp78 is a member of the Hsp104/Clp family with unknown function. Saccharomyces cerevisiae deletion mutants of HSP78 show wild-type like growth. We report that deletion of the HSP78 gene in yeast strains with point mutations in the SSC1 gene (encoding matrix Hsp70) led to loss of mitochondrial DNA, indicating that at least one of the heat shock proteins Hsp78 and mt-Hsp70 is needed to maintain a rho+ state of the mitochondrial genome. Mitochondria isolated from these double mutants had a strongly reduced membrane potential, explaining defects in the rate of preprotein import. The lack of Hsp78 led to aggregation of the mutant mt-Hsp70 while other matrix chaperones stayed soluble. We conclude that Hsp78 is required to keep mutant forms of mt-Hsp70 soluble and suggest a cooperation of Hsp78 and mt-Hsp70 in maintenance of essential mitochondrial functions.
线粒体热休克蛋白Hsp78是功能未知的Hsp104/Clp家族成员。HSP78基因的酿酒酵母缺失突变体表现出野生型生长。我们报道，在SSC1基因（编码线粒体基质Hsp70）存在点突变的酵母菌株中删除HSP78基因会导致线粒体DNA丢失，这表明热休克蛋白Hsp78和线粒体Hsp70中至少有一个对于维持线粒体基因组的ρ+状态是必需的。从这些双突变体中分离出的线粒体膜电位大幅降低，这解释了前体蛋白导入速率的缺陷。Hsp78的缺失导致突变型线粒体Hsp70聚集，而其他线粒体基质伴侣蛋白仍保持可溶状态。我们得出结论，Hsp78是使突变形式的线粒体Hsp70保持可溶状态所必需的，并表明Hsp78和线粒体Hsp70在维持线粒体基本功能方面存在协同作用。
