Ohba M
Mitsubishi-Kasei Institute of Life Sciences, Machida-shi, Tokyo, Japan.
FEBS Lett. 1997 Jun 9;409(2):307-11. doi: 10.1016/s0014-5793(97)00535-8.
In prokaryotes, DnaK-DnaJ chaperon is involved in the protein degradation catalyzed by proteases La and ClpA/B complex as shown in E. coli. To extend this into eukaryotic cells, we examined the effects of hsp70 genes, SSA1 and SSB1, and DnaJ genes, SIS1 and YDJ1, on the growth of proteasome subunit mutants of the yeast S. cerevisiae. The results identified SSB1 and SIS1 as a pair of chaperon genes specifically involved in efficient protein turnover in the yeast, whose overexpression suppressed the growth defects caused by the proteasome mutations. Moreover, a single amino acid substitution in the putative peptide-binding site of SSB1 protein profoundly enhanced the suppression activity, indicating that the activity is mediated by the peptide-binding activity of this chaperon. Thus SSB1, with its partner DnaJ, SIS1, modulates the efficiency of protein turnover through its chaperon activity.
在原核生物中，如大肠杆菌所示，DnaK-DnaJ伴侣蛋白参与由蛋白酶La和ClpA/B复合物催化的蛋白质降解过程。为了将此研究扩展到真核细胞，我们检测了热休克蛋白70基因SSA1和SSB1以及DnaJ基因SIS1和YDJ1对酿酒酵母蛋白酶体亚基突变体生长的影响。结果确定SSB1和SIS1是一对特别参与酵母中高效蛋白质周转的伴侣蛋白基因，它们的过表达抑制了由蛋白酶体突变引起的生长缺陷。此外，SSB1蛋白假定的肽结合位点中的单个氨基酸取代显著增强了抑制活性，表明该活性是由这种伴侣蛋白的肽结合活性介导的。因此，SSB1与其伴侣DnaJ（即SIS1）通过其伴侣活性调节蛋白质周转的效率。
