The effect of Mg2+ and calmidazolium on the calmodulin binding to inside-out vesicles of the human red cell membrane.

Calmodulin binds to inside-out vesicles of the human red cell membrane in a Ca2+-dependent manner. Mg2+ was found to be essential to this binding, half maximum binding occurring at decreasing Ca2+ concentration with increasing Mg2+ concentration. The calmodulin antagonist calmidazolium strongly reduced the Ca2+-dependent binding of calmodulin to the inside-out vesicles.