Functional interaction of cytosolic hsp70 and a DnaJ-related protein, Ydj1p, in protein translocation in vivo.
Functional interaction of cytosolic hsp70 and a DnaJ-related protein, Ydj1p, in protein translocation in vivo.
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胞浆 hsp70 和 DnaJ 相关蛋白 Ydj1p 在体内蛋白质易位中的功能相互作用。
DOI：
10.1128/mcb.16.8.4378
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发表时间：
1996
影响因子：
5.3
通讯作者：
Craig,EA
中科院分区：
文献类型：
--
作者：
Becker,J;Walter,W;Yan,W;Craig,EA
为了分析酿酒酵母胞质70 kDa热休克蛋白（hsps）的SSA 1类在体内的作用，我们分离了SSA 1的温度敏感突变体。评估了突变体细胞（ssa 1 tssa 2 ssa 3 ssa 4）从23°C的允许温度到37°C的非允许温度的转变对转运到内质网或线粒体中的几种前体蛋白的加工的影响。在所测试的三种线粒体蛋白质中，只有一种蛋白质的加工过程受到显著影响，即F1 F0 ATP酶的β亚基。在6种进入内质网的蛋白质中，只有前α因子原和蛋白酶A的转运受到抑制。前α因子原的加工在温度升至37°C后2 min内受到抑制，表明hsp 70缺陷对易位有直接影响。超过50%的放射性标记α-因子以前体形式积累，其余的迅速达到成熟形式。然而，易位阻断是完全的，因为前体形式不能通过易位途径被追踪。由于已知DnaJ相关蛋白与hsp 70相互作用，而AdnaJ相关基因YDJ 1条件突变的菌株在前α因子原转位方面存在缺陷，因此我们在体内寻找SSA基因与YDJ 1之间的遗传相互作用。我们发现YDJ 1的一个缺失突变在assa 1 tssa 2ssa 3ssa 4背景下是合成致死的。此外，含有单一功能SSA 1基因和YDJ 1缺失的菌株积累了α-因子的前体形式。然而，没有观察到YDJ 1突变和SSB基因突变之间的遗传相互作用，SSB基因编码第二类细胞溶质hsp 70分子伴侣。这些结果与SSA蛋白和Ydj 1 p在易位过程中共同作用的结果一致。
In order to analyze the in vivo role of theSSAclass of cytosolic 70-kDa heat shock proteins (hsps) ofSaccharomyces cerevisiae, we isolated a temperature-sensitive mutant ofSSA1. The effect of a shift of mutant cells (ssa1tsssa2 ssa3 ssa4) from the permissive temperature of 23°C to the nonpermissive temperature of 37°C on the processing of several precursor proteins translocated into the endoplasmic reticulum or mitochondria was assessed. Of three mitochondrial proteins tested, the processing of only one, the β subunit of the F1F0ATPase, was dramatically affected. Of six proteins destined for the endoplasmic reticulum, the translocation of only prepro-α-factor and proteinase A was inhibited. The processing of prepro-α-factor was inhibited within 2 min of the shift to 37°C, suggesting a direct effect of the hsp70 defect on translocation. More than 50% of radiolabeled α-factor accumulated in the precursor form, with the remainder rapidly reaching the mature form. However, the translocation block was complete, as the precursor form could not be chased through the translocation pathway. Since DnaJ-related proteins are known to interact with hsp70s and strains containing conditional mutations in adnaJ-related gene,YDJ1, are defective in translocation of prepro-α-factor, we looked for a genetic interaction betweenSSAgenes andYDJ1in vivo. We found that a deletion mutation of YDJ1 was synthetically lethal in assa1tsssa2 ssa3 ssa4background. In addition, a strain containing a single functionalSSAgene,SSA1, and a deletion ofYDJ1accumulated the precursor form of α-factor. However, no genetic interaction was observed between aYDJ1mutation and mutations in theSSBgenes, which encode a second class of cytosolic hsp70 chaperones. These results are consistent withSSAproteins and Ydj1p acting together in the translocation process.