Please use this identifier to cite or link to this item: http://ahro.austin.org.au/austinjspui/handle/1/9779
Title: Agonist binding and activation of the rat beta(1)-adrenergic receptor: role of Trp(134(3.28)), Ser(190(4.57)) and Tyr(356(7.43)).
Authors: Rezmann-Vitti, Linda A;Louis, Simon N S;Nero, Tracy L;Jackman, Graham P;Iakovidis, Dimitri;Machida, Curtis A;Louis, William J
Affiliation: Department of Medicine, Clinical Pharmacology and Therapeutics Unit, The University of Melbourne, Austin Health, Heidelberg 3084, Vic., Australia.
Issue Date: 15-Aug-2004
Citation: Biochemical Pharmacology; 68(4): 675-88
Abstract: We investigated the role of Trp(134(3.28)), Ser(190(4.57)) and Tyr(356(7.43)) in agonist binding to, and activation of, the rat beta(1)-adrenergic receptor by comparing pK(i)s and functional responses of W134A, S190A and Y356F mutant receptors to wild type, all stably expressed in CHO cells. All three mutations significantly (P < 0.05) reduced adenylyl cyclase intrinsic activity (IA) compared to wild type in response to stimulation with both (-)-isoprenaline (53-88%) and (-)-RO363 (46-61%), and there was no significant correlation either between IA or pD(2) and pK(i) (P > 0.4), suggesting that changes in pK(i) were not sufficient to explain the fall in adenylyl cyclase activity. The most pronounced reduction in affinity (126-fold, P < 0.01) was displayed by xamoterol for the Y356F mutation, suggesting that xamoterol is able to directly interact with Tyr(356(7.43)). For the other agonists, the change in pK(i) values for the mutant receptors ranged from a 20-fold decrease to a 2-fold increase compared to the wild type. In a three-dimensional model of the rat beta(1)-adrenergic receptor, Trp(134(3.28)) and Tyr(356(7.43)) form part of a hydrophobic binding pocket involving residues in transmembrane helices 1, 2, 3 and 7. Our results suggest that Trp(134(3.28)) and Tyr(356(7.43)), together with Trp(353(7.40)), are able to interact via pi-pi interactions to stabilize the extracellular ends of transmembrane helices 3 and 7. Ser(190(4.57)) appears to be involved in a hydrogen bonding network, which maintains the spatial relationship between transmembrane helices 3 and 4. These interhelical interactions suggest that the three mutated residues stabilize the active receptor state by maintaining the proper packing of their respective transmembrane helix within the helix bundle, facilitating the appropriate movement and rotation of the transmembrane regions during the activation process.
Internal ID Number: 15276075
URI: http://ahro.austin.org.au/austinjspui/handle/1/9779
DOI: 10.1016/j.bcp.2004.04.021
URL: http://www.ncbi.nlm.nih.gov/pubmed/15276075
Type: Journal Article
Subjects: Adrenergic Agonists.pharmacology
Amino Acid Sequence
Animals
CHO Cells
Cricetinae
Cyclic AMP.metabolism
Humans
Molecular Sequence Data
Mutation
Radioligand Assay
Rats
Receptors, Adrenergic, beta-1.drug effects.genetics.metabolism
Sequence Homology, Amino Acid
Serine.metabolism
Tryptophan.metabolism
Tyrosine.metabolism
Appears in Collections:Journal articles

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