Specifically phosphorylates the agonist-occupied form of the beta-adrenergic and closely related receptors. [beta-adrenergic receptor] + ATP = [beta-adrenergic receptor]-phosphate + ADP + H(+) Interacts with GIT1. Ubiquitous; brain, spleen > heart, lung > kidney. Ubiquitinated. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. GPRK subfamily.