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The small heat‐shock protein Hsp26 of Saccharomyces cerevisiae assembles into a high molecular weight aggregate
Author(s) -
Bentley Nicola J.,
Fitch Ian T.,
Tuite Mick F.
Publication year - 1992
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.320080204
Subject(s) - biology , heat shock protein , saccharomyces cerevisiae , differential centrifugation , yeast , centrifugation , biochemistry , hspa14 , molecular mass , gene , enzyme , hsp70
Hsp26 is one the major small heat‐shock proteins (Hsp) of the Saccharomyces cerevisiae . yet its cellular role remains to be discovered. To examine the cellular consequences of overexpression of Hsp26, the gene encoding this protein ( HSP26 ) was overexpressed from a multicopy plasmid using either its own promoter or by coupling it to the effecient constitutive PGK promoter. The PGK promoter provided the opportunity to overexpress Hsp26 under nonstress conditions and such high level synthesis, prior to a lethal heat shock (50°C), gave a small but reproducible elevation in thermotolerance. In transformed strains overexpressing Hsp26 under either stressed or non‐stress conditions, the Hsp26 polypeptide was recovered almost exclusively as a high molecular weight aggregate. This high molecular weight aggregate (or heat‐shock granule, HSG) was purified by differential centrifugation and sucrose gradient density centrifugation and shown, by electron microscopic analysis, to be of a uniform size (15–25 nm diameter). Analysis of the purified HSG demonstrated that it had a molecular weight of 550 kDa, yet contained no other integral polypeptides or other macromolecules.