β-Adrenergic Receptor Kinase: Primary Structure Delineates a Multigene Family

TLDR

The beta‑adrenergic receptor kinase (beta‑ARK) specifically phosphorylates agonist‑occupied beta‑adrenergic receptors and is important for rapid, agonist‑specific desensitization. Its structure was determined by isolating bovine brain cDNA clones using oligonucleotide probes derived from a partial amino‑acid sequence. The beta‑ARK cDNA encodes a 689‑amino‑acid, 79.7‑kDa protein with a kinase domain most similar to PKC and PKA, and expression in COS‑7 cells produced a protein that strongly phosphorylates agonist‑occupied β2‑adrenergic receptors and weakly phosphorylates bleached rhodopsin; RNA blotting revealed a 4‑kb mRNA most abundant in brain and spleen, while genomic analysis indicates beta‑ARK is likely the first member of a multigene family of receptor kinases.

Abstract

The beta-adrenergic receptor kinase (beta-ARK), which specifically phosphorylates only the agonist-occupied form of the beta-adrenergic and closely related receptors, appears to be important in mediating rapid agonist-specific (homologous) desensitization. The structure of this enzyme was elucidated by isolating clones from a bovine brain complementary DNA library through the use of oligonucleotide probes derived from partial amino acid sequence. The beta-ARK cDNA codes for a protein of 689 amino acids (79.7 kilodaltons) with a protein kinase catalytic domain that bears greatest sequence similarity to protein kinase C and the cyclic adenosine monophosphate (cyclic AMP)--dependent protein kinase. When this clone was inserted into a mammalian expression vector and transfected into COS-7 cells, a protein that specifically phosphorylated the agonist-occupied form of the beta 2-adrenergic receptor and phosphorylated, much more weakly, the light-bleached form of rhodopsin was expressed. RNA blot analysis revealed a messenger RNA of four kilobases with highest amounts in brain and spleen. Genomic DNA blot analysis also suggests that beta-ARK may be the first sequenced member of a multigene family of receptor kinases.