Sugar-Induced Molten-Globule Model

Proteins denature at low pH because of intramolecular electrostatic repulsions. The addition of salt partially overcomes this repulsion for some proteins, yielding a collapsed conformation called the A-state. A-states have characteristics expected for the molten globule, a notional kinetic protein f...

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Bibliographic Details
Published in:Biochemistry (Easton) 1998-12, Vol.37 (48), p.17048-17053
Main Authors: Davis-Searles, Paula R, Morar, Artemiza S, Saunders, Aleister J, Erie, Dorothy A, Pielak, Gary J
Format: Article
Language:English
Subjects:
Animals
Carbohydrates
Circular Dichroism
Cytochrome c Group - chemistry
Deuterium
Horses
Hydrogen
Nuclear Magnetic Resonance, Biomolecular
Protein Folding
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Summary:Proteins denature at low pH because of intramolecular electrostatic repulsions. The addition of salt partially overcomes this repulsion for some proteins, yielding a collapsed conformation called the A-state. A-states have characteristics expected for the molten globule, a notional kinetic protein folding intermediate. Here we show that the addition of neutral sugars to solutions of acid-denatured equine ferricytochrome c induces formation of the A-state in the absence of added salt. We characterized the structure and stability of the sugar-induced A-state with circular dichroism spectropolarimetry (CD) and NMR-monitored hydrogen−deuterium exchange experiments. We also examined the stability of the sugar-induced A-state as a function of sugar size and concentration. The results are interpreted using several models and we conclude that the stabilizing effect is consistent with increased steric repulsion between the protein and the sugar solutions.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi981364v