JBC, Vol. 250, Issue 15, 6022-6025, Aug, 1975
Nonequivalence of the metal binding sites of conalbumin. Calorimetric and spectrophotometric studies of aluminum binding
J. W. Donovan and K. D. Ross
Differential scanning calorimetric experiments show that addition of
Al(III) to conalbumin increases its denaturation temperature by 5 degrees,
from 60 to 68 degrees. Only one Al(III) bound per conalbumin molecule
produces this change in heat stability; additional bound Al(III) does not
affect the heat stability. Since Al(III) displaces both Cu(II) bound at the
metal binding sites of conalbumin, binding of aluminum takes place at the
same metal binding sites. The binding constant for the second Al(III) is at
least 100-fold less than that for the binding of the first Al(III), and
both are displaced by added iron. The order of increasing heat stability of
the metal ion complexes of conalbumin, Cu(II), Al(III), Fe(III), is the
order of increasing binding constant for these metal ions.