Zea mays CCaMK: autophosphorylation-dependent substrate phosphorylation and down-regulation by red light

The role of protein kinases has been extensively studied in various signal transduction pathways and they are one of the most important components that link the signal perception to the final response. However, not many studies have been reported, especially from the plant systems, that show the regulation pattern of the kinase itself under different conditions. A calcium/calmodulin-dependent protein kinase has already been purified and characterized from etiolated maize coleoptiles. In this paper a detailed study of how the kinase itself is regulated at the autophosphorylation level is provided. Evidence is also given that the autophosphorylation of kinase effects its activity towards substrate phosphorylation. It is further shown that the kinase is an important component of the light signalling pathway as the level of the kinase itself decreases by red light irradiation.