Folding in vivo of a newly translated yeast cytosolic enzyme is mediated by the SSA class of cytosolic yeast Hsp70 proteins

Suwon Kim, Brenda Schilke, Elizabeth A. Craig, Arthur L. Horwich

Research output: Contribution to journalArticle

55 Scopus citations

Abstract

The nature of chaperone action in the eukaryotic cytosol that assists newly translated cytosolic proteins to reach the native state has remained poorly defined. Actin, tubulin, and Gα transducin are assisted by the cytosolic chaperonin, CCT, but many other proteins, for example, ornithine transcarbamoylase (OTC), a cytosolic homotrimeric enzyme of yeast, do not require CCT action. Here, we observe that yeast cytosolic OTC is assisted to its native state by the SSA class of yeast cytosolic Hsp70 proteins. In vitro, refolding of OTC diluted from denaturant was assisted by crude yeast cytosol and ATP and found to be directed by SSA1/2. In vivo, when OTC was induced in a temperature-sensitive SSA-deficient strain, it exhibited reduced specific activity, and nonnative subunits were detected in the soluble fraction. These findings indicate that, in vivo, the Hsp70 system assists in folding at least some newly translated cytosolic enzymes, most likely functioning in a posttranslational manner.

Original languageEnglish (US)
Pages (from-to)12860-12865
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume95
Issue number22
DOIs
StatePublished - Oct 27 1998
Externally publishedYes

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