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Differential temperature-dependent chaperone-like activity of alphaA- and alphaB-crystallin homoaggregates.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 1999 Dec 03; Vol. 274 (49), pp. 34773-8. - Publication Year :
- 1999
-
Abstract
- alpha-Crystallin, a heteromultimeric protein made up of alphaA- and alphaB-crystallins, functions as a molecular chaperone in preventing the aggregation of proteins. We have shown earlier that structural perturbation of alpha-crystallin can enhance its chaperone-like activity severalfold. The two subunits of alpha-crystallin have extensive sequence homology and individually display chaperone-like activity. We have investigated the chaperone-like activity of alphaA- and alphaB-crystallin homoaggregates against thermal and nonthermal modes of aggregation. We find that, against a nonthermal mode of aggregation, alphaB-crystallin shows significant protective ability even at subphysiological temperatures, at which alphaA-crystallin or heteromultimeric alpha-crystallin exhibit very little chaperone-like activity. Interestingly, differences in the protective ability of these homoaggregates against the thermal aggregation of beta(L)-crystallin is negligible. To investigate this differential behavior, we have monitored the temperature-dependent structural changes in both the proteins using fluorescence and circular dichroism spectroscopy. Intrinsic tryptophan fluorescence quench-ing by acrylamide shows that the tryptophans in alphaB-crystallin are more accessible than the lone tryptophan in alphaA-crystallin even at 25 degrees C. Protein-bound 8-anilinonaphthalene-1-sulfonate fluorescence demonstrates the higher solvent accessibility of hydrophobic surfaces on alphaB-crystallin. Circular dichroism studies show some tertiary structural changes in alphaA-crystallin above 50 degrees C. alphaB-crystallin, on the other hand, shows significant alteration of tertiary structure by 45 degrees C. Our study demonstrates that despite a high degree of sequence homology and their generally accepted structural similarity, alphaB-crystallin is much more sensitive to temperature-dependent structural perturbation than alphaA- or alpha-crystallin and shows differences in its chaperone-like properties. These differences appear to be relevant to temperature-dependent enhancement of chaperone-like activity of alpha-crystallin and indicate different roles for the two proteins both in alpha-crystallin heteroaggregate and as separate proteins under stress conditions.
- Subjects :
- Acrylamide pharmacology
Anilino Naphthalenesulfonates pharmacology
Animals
Cattle
Circular Dichroism
Dithiothreitol pharmacology
Dose-Response Relationship, Drug
Fluorescent Dyes pharmacology
Kinetics
Protein Binding drug effects
Protein Structure, Secondary drug effects
Protein Structure, Tertiary drug effects
Temperature
Time Factors
Crystallins metabolism
Molecular Chaperones metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 274
- Issue :
- 49
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 10574947
- Full Text :
- https://doi.org/10.1074/jbc.274.49.34773