Calcium/calmodulin-dependent phosphorylation and the effect of cadmium in cultured fish cells

1. Calmodulin constitutes approximately 0.7% of the soluble protein in rainbow trout gonadal cells (RTG-2). 2. Calcium-dependent phosphorylation of endogenous proteins was examined in vitro in cytosol fractions of RTG-2 cells. Phosphorylation of numerous proteins was stimulated by calmodulin and calcium, and inhibited by the calmodulin-binding phenothiazine, trifluoperazine. 3. Cadmium was as effective as calcium in stimulating calmodulin-dependent phosphorylations of endogenous substrates in cytosolic fractions of RTG-2 cells.