Pejman Ghanouni

Publication Details

  • Agonist-induced conformational changes in the G-protein-coupling domain of the beta(2) adrenergic receptor PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Ghanouni, P., Steenhuis, J. J., Farrens, D. L., Kobilka, B. K. 2001; 98 (11): 5997-6002


    The majority of extracellular physiologic signaling molecules act by stimulating GTP-binding protein (G-protein)-coupled receptors (GPCRs). To monitor directly the formation of the active state of a prototypical GPCR, we devised a method to site specifically attach fluorescein to an endogenous cysteine (Cys-265) at the cytoplasmic end of transmembrane 6 (TM6) of the beta(2) adrenergic receptor (beta(2)AR), adjacent to the G-protein-coupling domain. We demonstrate that this tag reports agonist-induced conformational changes in the receptor, with agonists causing a decline in the fluorescence intensity of fluorescein-beta(2)AR that is proportional to the biological efficacy of the agonist. We also find that agonists alter the interaction between the fluorescein at Cys-265 and fluorescence-quenching reagents localized to different molecular environments of the receptor. These observations are consistent with a rotation and/or tilting of TM6 on agonist activation. Our studies, when compared with studies of activation in rhodopsin, indicate a general mechanism for GPCR activation; however, a notable difference is the relatively slow kinetics of the conformational changes in the beta(2)AR, which may reflect the different energetics of activation by diffusible ligands.

    View details for Web of Science ID 000168883700014

    View details for PubMedID 11353823

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