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J Biol Chem. 2003 Mar 21;278(12):10763-9. Epub 2003 Jan 17.

Thermal aggregation of ribonuclease A. A contribution to the understanding of the role of 3D domain swapping in protein aggregation.

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  • 1Dipartimento di Scienze Neurologiche e della Visione, Sezione di Chimica Biologica, Facolt√† di Medicina e Chirurgia, Universit√† di Verona, Strada Le Grazie 8, Italy.

Abstract

By lyophilizing RNase A from 40% acetic acid solutions, two dimeric aggregates, the "minor" and "major" dimers (named here N-dimer and C-dimer, respectively), form by 3D domain swapping at a ratio of 1:4. Trimeric and tetrameric aggregates are also obtained. The two dimers and the higher oligomers also form without a lyophilization step. By keeping RNase A dissolved at a high concentration (generally 200 mg/ml) in various media at temperatures ranging from 23 to 70 degrees C for times varying from a few minutes to 2 h, various oligomers, in particular the two dimeric conformers, formed in quite different amounts, often inverting their relative quantities depending on the more or less severe unfolding conditions. When unfolding mainly concerned the N terminus of the protein, richer in hydrophilic residues, the N-dimer, formed by 3D domain swapping of the N-terminal alpha-helix of each monomer, prevailed over the C-dimer. Under more vigorous denaturing conditions, where also the C terminus of RNase A, richer in hydrophobic amino acids, unfolded, the C-dimer, formed by 3D domain swapping of the C-terminal beta-strand, prevailed over the other, possibly because of the induction to aggregation promoted by the hydrophobic residues present in the C termini of the two monomers.

PMID:
12533538
[PubMed - indexed for MEDLINE]
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