Analysis of the calcium-dependent interaction of calmodulin with bovine serum albumin.

An air-driven ultracentrifuge has been used to investigate the calcium-dependent association between calmodulin and bovine serum albumin. Procedures were described which allowed the interaction to be analyzed to yield the equilibrium constant. At low ionic strength (25 mM Tris-HCl, pH 7.5, pCa 6.68, 9 degrees C) the equilibrium constant for the interaction was estimated to be 2.1 X 10(4) M-1, while at high ionic strength (25 mM Tris-HCl, pH 7.5, 150 mM KCl, pCa 6.68, 9 degrees C) the value was 4.5 X 10(3) M-1. Under similar conditions, calmodulin was also found to interact with beta-lactoglobulin A and gelatin, but no detectable association was observed with ovalbumin.