Thermodynamics of unfolding of the all beta-sheet protein interleukin-1 beta.
The thermal denaturation of interleukin-1 beta in solution has been studied by differential scanning calorimetry at various pH values. It is shown that the thermal transition of interleukin-1 beta is completely reversible below pH 2.5, only partly reversible in the pH range 2.5-3.5, and irreversible above pH 3.5. Analysis of the reversible unfolding of interleukin-1 beta shows that the heat denaturation is well approximated by a two-state transition and is accompanied by a significant increase of heat capacity. The partial heat capacity of denatured interleukin-1 beta is very close to that expected for the completely unfolded protein. This permitted us to assign the thermodynamic characteristics of interleukin-1 beta denaturation to its complete unfolding and to correlate them with structural features of the protein. The contributions of hydrogen bonding and hydrophobic interactions to the stability of interleukin-1 beta are analyzed and compared to those for other globular proteins. It is shown that the Gibbs energy of a hydrogen bond in a beta-sheet structure is greater than in alpha-helices.
Makhatadze
G I
GI
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
Clore
G M
GM
Gronenborn
A M
AM
Privalov
P L
PL
D002152:Calorimetry, Differential Scanning / Q000379:methods; D003001:Cloning, Molecular; D004926:Escherichia coli; D006801:Humans; D006860:Hydrogen Bonding; D007375:Interleukin-1 / Q000737:chemistry*; D008433:Mathematics; D008962:Models, Theoretical; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry
D007375:Interleukin-1; D011994:Recombinant Proteins