Document Detail

Hsc66 and Hsc20, a new heat shock cognate molecular chaperone system from Escherichia coli.
MedLine Citation:
PMID:  9144776     Owner:  NLM     Status:  MEDLINE    
The hscA and hscB genes of Escherichia coli encode novel chaperone and co-chaperone proteins, designated Hsc66 and Hsc20, respectively. We have overproduced and purified Hsc66 and Hsc20 in high yield in E. coli and describe their initial characterization including absorbance, fluorescence, and circular dichroism spectra. Immunoblot analyses of E. coli cultures using antisera to Hsc66 and Hsc20 raised in rabbits establish that Hsc66 and Hsc20 are constitutively expressed at levels corresponding to cell concentration approximately 20 microM and approximately 10 microM, respectively. The levels do not change appreciably following heat shock (44 degrees C), but a small increase in Hsc20 is observed following a shift to 10 degrees C. Purified Hsc66 exhibits a low intrinsic ATPase activity (approximately 0.6 min-1 at 37 degrees C), and Hsc20 was found to stimulate this activity up to 3.8-fold with half-maximal stimulation at a concentration approximately 5 microM. These findings suggest that Hsc66 and Hsc20 comprise a molecular chaperone system similar to the prokaryotic DnaK/DnaJ and eukaryotic hsp70/hsp40 systems. Sequence differences between Hsc66 and Hsc20 compared to other members of this chaperone family, however, suggest that the Hsc66/Hsc20 system will display different peptide binding specificity and that it is likely to be subject to different regulatory mechanisms. The high level of constitutive expression and the lack of a major response to temperature changes suggest that Hsc66 and Hsc20 play an important cellular role(s) under non-stress conditions.
L E Vickery; J J Silberg; D T Ta
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Protein science : a publication of the Protein Society     Volume:  6     ISSN:  0961-8368     ISO Abbreviation:  Protein Sci.     Publication Date:  1997 May 
Date Detail:
Created Date:  1997-09-02     Completed Date:  1997-09-02     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  9211750     Medline TA:  Protein Sci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1047-56     Citation Subset:  IM    
Department of Physiology and Biophysics, University of California Irvine 92697, USA.
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MeSH Terms
Adenosine Triphosphatases / metabolism
Bacterial Proteins / biosynthesis,  chemistry,  isolation & purification
Chromatography, Gel
Circular Dichroism
Escherichia coli / genetics,  metabolism*
Escherichia coli Proteins*
Genes, Bacterial
HSP70 Heat-Shock Proteins / biosynthesis,  chemistry*,  isolation & purification
Heat-Shock Proteins / biosynthesis,  chemistry*,  isolation & purification
Molecular Chaperones*
Protein Conformation*
Recombinant Proteins / biosynthesis,  chemistry,  isolation & purification
Spectrometry, Fluorescence
Grant Support
Reg. No./Substance:
0/Antibodies; 0/Bacterial Proteins; 0/Escherichia coli Proteins; 0/HSP70 Heat-Shock Proteins; 0/Heat-Shock Proteins; 0/HscB protein, E coli; 0/Molecular Chaperones; 0/Recombinant Proteins; 0/hscA protein, E coli; EC 3.6.1.-/Adenosine Triphosphatases

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