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AS‐48: a circular protein with an extremely stable globular structure
Author(s) -
Cobos E.S,
Filimonov V.V,
Gálvez A,
Maqueda M,
Valdı́via E,
Martı́nez J.C,
Mateo P.L
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02841-1
Subject(s) - globular protein , differential scanning calorimetry , chemistry , ionic strength , enthalpy , gibbs free energy , crystallography , calorimetry , thermodynamics , heat capacity , protein folding , native state , ionic bonding , denaturation (fissile materials) , chemical stability , biochemistry , organic chemistry , ion , nuclear chemistry , physics , aqueous solution
The unfolding thermodynamics of the circular enterocin protein AS‐48, produced by Enterococcus faecalis , has been characterized by differential scanning calorimetry. The native structure of the 70‐residue protein is extremely thermally stable. Thus, at pH 2.5 and low ionic strength thermal denaturation occurs under equilibrium at 102°C, while the unfolded state irreversibly aggregates at neutral and alkaline pH. Calorimetric data analysis shows that the specific enthalpy change upon unfolding is unusually small and the heat capacity change is quite normal for a protein of this size, whereas the Gibbs energy change at 25°C is relatively high. At least part of this high stability might be put down to entropic constraints induced by the circular organization of the polypeptide chain.