PURIFICATION AND FUNCTIONAL-CHARACTERIZATION OF BETA-ADRENERGIC-RECEPTOR KINASE EXPRESSED IN INSECT CELLS

The beta-adrenergic receptor kinase mediates agonist-dependent phospho rylation of beta-adrenergic receptors, which is thought to represent t he first step of homologous desensitization. We have expressed bovine and human betaARK1 in Sf9 cells and purified them to apparent homogene ity in milligram quantities. The K(m)-values of the enzyme were 3.8 mu M for rhodopsin and 22 muM for ATP; the V(max)-value was 9.9 mol phosp hate/mol betaARK/min. These data indicate that the two recombinant kin ases were at least as active as preparations previously obtained from bovine brain. There were no differences in the functional activity of human and bovine betaARK.