Structural alteration of Escherichia coli Hsp31 by thermal unfolding increases chaperone activity

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Escherichia coli Hsp31, encoded by hchA, is a heat-inducible molecular chaperone. We found that Hsp31 undergoes a conformational change via temperature-induced unfolding, generating a high molecular weight (HMW) form with enhanced chaperone activity. Although it has previously been reported that some subunits of the Hsp31 crystal structure show structural heterogeneity with increased hydrophobic surfaces, Hsp31 basically forms a dimer. We found that a C-terminal deletion (C Delta 19) of Hsp31 exhibited structurally and functionally similar characteristics to that of the HMW form. Both the C Delta 19 and HMW forms achieved a structure with considerably more p-sheets and less a-helices than the native dimeric form, exposing a portion of its hydrophobic surfaces. The structural alterations were determined from its spectral changes in circular dichroism, intrinsic fluorescence of tryptophan residues, and fluorescence of bis-ANS binding to a hydrophobic surface. Interestingly, during thermal transition, the dimeric Hsp31 undergoes a conformational change to the HMW species via the C Delta 19 structure, as monitored with near-UV CD spectrum, implying that the C Delta 19 resembles an intermediate state between the dimer and the HMW form. From these results, we propose that Hsp31 transforms itself into a fully functional chaperone by altering its tertiary and quatemary structures. (C) 2012 Elsevier B.V. All rights reserved.
Publisher
ELSEVIER SCIENCE BV
Issue Date
2013-02
Language
English
Article Type
Article
Keywords

MOLECULAR CHAPERONE; CRYSTAL-STRUCTURE; REGULATED CHAPERONE; ALPHA-CRYSTALLIN; HUMAN DJ-1; PROTEIN; STRESS; OLIGOMERIZATION; TEMPERATURES; REVEALS

Citation

BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS, v.1834, no.2, pp.621 - 628

ISSN
1570-9639
DOI
10.1016/j.bbapap.2012.11.006
URI
http://hdl.handle.net/10203/174874
Appears in Collection
BS-Journal Papers(저널논문)
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