title: Identification, purification, and characterization of GRK5, a member of the family of G protein-coupled receptor kinases.
abstract: A novel member of the family of G protein-coupled receptor kinases (GRKs), named GRK5, has been cloned from bovine taste epithelium. The cDNA sequence predicts a 590-amino acid protein with high overall similarity to rhodopsin kinase. GRK5 mRNA is found most abundantly in lung, heart, retina, and lingual epithelium, but is expressed very little in brain, liver, kidney, or testis. GRK5 expressed in Sf9 cells was purified to apparent homogeneity. GRK5 major autophosphorylation sites were mapped to Ser484 and Thr485. Purified GRK5 phosphorylates rhodopsin in a light-dependent manner and beta 2-adrenergic receptor in an agonist-dependent manner and phosphorylates the C-terminal tail regions of both receptor proteins. GRK5 possesses neither a CAAX motif specifying protein prenylation like rhodopsin kinase nor similarity to the G protein beta gamma-subunit binding domain of beta-adrenergic receptor kinases. GRK5 phosphorylation of rhodopsin or beta 2-adrenergic receptor is not stimulated by G protein beta gamma-subunits. The GRK5 protein does not undergo agonist-dependent translocation from cytosol to membranes as do beta-adrenergic receptor kinase and rhodopsin kinase, but rather appears to associate with membranes constitutively. GRK5 thus appears functionally similar to other characterized GRKs, but has distinct regulatory properties which may be important for its cellular function.
authors.affiliation: Howard Hughes Medical Institute, Durham, North Carolina.
authors.forename: R T
authors.initials: RT
authors.lastname: Premont
authors.forename: W J
authors.initials: WJ
authors.lastname: Koch
authors.forename: J
authors.initials: J
authors.lastname: Inglese
authors.forename: R J
authors.initials: RJ
authors.lastname: Lefkowitz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D054774:G-Protein-Coupled Receptor Kinase 5; D019204:GTP-Binding Proteins / Q000096:biosynthesis*; D008297:Male; D008969:Molecular Sequence Data; D009061:Mouth Mucosa / Q000378:metabolism; D009928:Organ Specificity; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D015183:Restriction Mapping; D012243:Rhodopsin / Q000378:metabolism; D012694:Serine; D013649:Taste / Q000502:physiology; D013912:Threonine
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D010446:Peptide Fragments; D012333:RNA, Messenger; D013912:Threonine; D012694:Serine; D012243:Rhodopsin; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D054774:G-Protein-Coupled Receptor Kinase 5; D019204:GTP-Binding Proteins