FIGURE 2.

Ca²⁺/calmodulin regulates the kinase activity of CRLK1. A, kinase activity of M28–392 and M28–369 at different concentrations of CaM and CaM antagonist CPZ. Inhibition of Ca²⁺/CaM-stimulated CRLK1 activity by CPZ was measured in the presence of 200 nm Ca²⁺/CaM. B, CaM does not stimulate the kinase activity of M28–369. C, plant CaM isoforms differentially regulate CRLK activity. Bovine serum albumin (BSA) was used as a negative control. D and E, substrate phosphorylaton for M28–392 and M28–369 at different concentrations of CaM and CaM antagonist CPZ. F, phosphoamino acid analysis showing that M28–440 autophosphorylates at serine and threonine residues.