Thermodynamics of Mn(2+)-binding to goat alpha-lactalbumin.
By means of reaction calorimetry we measured the apparent enthalpy change, delta Happ, of the binding of Mn(2+)-ions to goat alpha-lactalbumin as a function of temperature. The observed delta Happ can be written as the sum of contributions resulting from a conformational and a binding process. In combination with the thermal unfolding curve of goat alpha-lactalbumin, we succeeded in separating the complete set of thermodynamic parameters (delta H, delta G, delta S, delta Cp) into the binding and conformational contributions. By circular dichroism we showed that NH+4-ions, upon binding to bovine alpha-lactalbumin, induce the same conformational change as do Na+ and K+: the binding constant KappNH+4 equals 98 +/- 9 M-1.
Desmet
J
J
Interdisciplinary Research Center, Katholieke Universiteit Leuven, Kortrijk, Belgium.
Tieghem
E
E
Van Dael
H
H
Van Cauwelaert
F
F
D000818:Animals; D002151:Calorimetry / Q000379:methods; D002942:Circular Dichroism; D005260:Female; D006041:Goats; D007768:Lactalbumin / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008433:Mathematics; D008892:Milk; D011487:Protein Conformation; D013816:Thermodynamics
D008345:Manganese; D007768:Lactalbumin