BIP/KAR2P SERVES AS A MOLECULAR CHAPERONE DURING CARBOXYPEPTIDASE-Y FOLDING IN YEAST

被引:161
作者
SIMONS, JF
FERRONOVICK, S
ROSE, MD
HELENIUS, A
机构
[1] YALE UNIV,SCH MED,HOWARD HUGHES MED INST,NEW HAVEN,CT 06520
[2] PRINCETON UNIV,LEWIS THOMAS LAB,DEPT MOLEC BIOL,PRINCETON,NJ 08544
关键词
D O I
10.1083/jcb.130.1.41
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Although transiently associated with numerous newly synthesized proteins, BiP has not been shown to be an essential component directly linked to the folding and oligomerization of newly synthesized proteins in the endoplasmic reticulum. To determine whether it is needed as a molecular chaperone, we analyzed the maturation of an endogenous yeast glycoprotein, carboxypeptidase Y (CPY) in several yeast strains with temperature-sensitive mutations in BiP. These kar2 mutant strains have previously been found to be defective in translocation at the nonpermissive temperature (Vogel, J. P., L. M. Misra, and M. D. Rose. 1990. J. Cell Biol. 110:1885-1895). To circumvent the translocation block, we used DTT at permissive temperature to delay folding and intracellular transport. We then followed the maturation of the ER-retained CPY after shifting to the nonpermissive temperature and dilution of the DTT. Without the functional chaperone, CPY aggregated, failed to be oxidized, and remained in the ER. In contrast to wild-type cells, in which BiP binding was transient with no more than 10-15% of labeled CPY associated at any time, 30-100% of the CPY remained associated with BiP in the mutant strains. In a heterozygous diploid strain, CPY matured and exited the ER normally. Taken together, the results provide clear evidence that BiP plays a critical role as a molecular chaperone in CPY folding.
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页码:41 / 49
页数:9
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