THE EXTRACELLULAR DOMAIN OF CD4 RECEPTOR POSSESSES A PROTEIN-KINASE ACTIVITY

The CD4 receptor of T-helper cells is an essential participant in immu ne response formation and HIV infection. We report here that the extra cellular domains of CD4 receptor can catalyze the phosphotransferase ( kinase) reaction. Incubation of rsCD4 in solution,vith [gamma-P-32]ATP results in the Ca2+-dependent autophosphorylation of the protein pres umably at a His residue because the reaction is prevented by the dieth ylpyrocarbonate treatment. The rsCD4 phosphorylates milk casein or hum an plasma proteins as a Ser/Thr protein kinase. (C) 1998 Federation of European Biochemical Societies.