Binding of calcium ions to bovine beta-casein

The isotherms for Ca++ binding to bovine alpha-casein have been measured at 5 temperatures in the range 4-40 degrees C and at 4 different ionic strengths. The results are interpreted by an interactive-site binding model, and are compared with results previously obtained on alpha s1-casein. The affinity of beta-casein for the first Va2+ to bind is similar to the affinity of alpha s1-casein for the same binding event: however, binding of subsequent Ca2+ to beta-casein is weaker than the binding to alpha s1-casein. The results are discussed in terms of precipitability of the 2 caseins caused by the binding of Ca2+.