Regions of the alpha 1-adrenergic receptor involved in coupling to phosphatidylinositol hydrolysis and enhanced sensitivity of biological function.
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Regions of the hamster alpha 1-adrenergic receptor (alpha 1 AR) that are important in GTP-binding protein (G protein)-mediated activation of phospholipase C were determined by studying the biological functions of mutant receptors constructed by recombinant DNA techniques. A chimeric receptor consisting of the beta 2-adrenergic receptor (beta 2AR) into which the putative third cytoplasmic loop of the alpha 1AR had been placed activated phosphatidylinositol metabolism as effectively as the native alpha 1AR, as did a truncated alpha 1AR lacking the last 47 residues in its cytoplasmic tail. Substitutions of beta 2AR amino acid sequence in the intermediate portions of the third cytoplasmic loop of the alpha 1AR or at the N-terminal portion of the cytoplasmic tail caused marked decreases in receptor coupling to phospholipase C. Conservative substitutions of two residues in the C terminus of the third cytoplasmic loop (Ala293----Leu, Lys290----His) increased the potency of agonists for stimulating phosphatidylinositol metabolism by up to 2 orders of magnitude. These data indicate (i) that the regions of the alpha 1AR that determine coupling to phosphatidylinositol metabolism are similar to those previously shown to be involved in coupling of beta 2AR to adenylate cyclase stimulation and (ii) that point mutations of a G-protein-coupled receptor can cause remarkable increases in sensitivity of biological response.
SubjectAmino Acid Sequence
Molecular Sequence Data
Receptors, Adrenergic, alpha
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James B. Duke Distinguished Professor of Cell Biology
Studies of the mechanisms of action and regulation of hormones and neurotransmitters at the cellular and molecular levels constitute the main goals our of research activities. G protein-coupled receptors (GPCR) mediate the actions of signaling molecules from unicellular organisms to man. We have used adrenergic and dopamine receptors to characterize the structure/function and regulation mechanisms of these prototypes of G protein-coupled receptors. Another approach has been to characterize
James B. Duke Distinguished Professor of Medicine
Dr. Lefkowitz’s memoir, A Funny Thing Happened on the Way to Stockholm, recounts his early career as a cardiologist and his transition to biochemistry, which led to his Nobel Prize win. Robert J. Lefkowitz, M.D. is James B. Duke Professor of Medicine and Professor of Biochemistry and Chemistry at the Duke University Medical Center. He has been an Investigator of the
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