Aluminum increases phosphorylation of particular proteins in cellular suspension cultures of coffee (Coffea arabica)

Aluminum (Al) is the most abundant metal in the earth's crust and occurs in a number of different forms in the soil. Al toxicity is a global problem t hat limits crop productivity in acid soils. Coffee is a plant which grows i n soils with a high organic matter content, and AI is available in these so ils because they are acidic. In the present work, we demonstrate the effect of aluminum toxicity on the phosphorylation pattern of proteins. Coffea ar abica suspension cells were incubated with increasing concentrations of AlC l3 (200-1000 mu mol/L), and an in vitro phosphorylation reaction with cell extracts was performed. There was no change in the proteins present in extr acts from cells treated with AlCl3, compared with untreated cells. However, the protein phosphorylation patterns did change. The phosphorylated protei ns with a molecular mass of 18, 31 and 53 kDa increased dramatically after in vivo treatment of cells with AlCl3. When AlCl3 was added to the reaction mixture, no differences in phosphorylation patterns were observed. These r esults suggest that in vivo treatment of Coffea cells with AlCl3 affects th e activity of some protein kinases.