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Probing the role of the cation–π interaction in the binding sites of GPCRs using unnatural amino acids

Torrice, Michael M. and Bower, Kiowa S. and Lester, Henry A. and Dougherty, Dennis A. (2009) Probing the role of the cation–π interaction in the binding sites of GPCRs using unnatural amino acids. Proceedings of the National Academy of Sciences of the United States of America, 106 (29). pp. 11919-11924. ISSN 0027-8424. PMCID PMC2715518. doi:10.1073/pnas.0903260106.

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We describe a general application of the nonsense suppression methodology for unnatural amino acid incorporation to probe drug–receptor interactions in functional G protein-coupled receptors (GPCRs), evaluating the binding sites of both the M2 muscarinic acetylcholine receptor and the D2 dopamine receptor. Receptors were expressed in Xenopus oocytes, and activation of a G protein-coupled, inward-rectifying K^+ channel (GIRK) provided, after optimization of conditions, a quantitative readout of receptor function. A number of aromatic amino acids thought to be near the agonist-binding site were evaluated. Incorporation of a series of fluorinated tryptophan derivatives at W6.48 of the D2 receptor establishes a cation–π interaction between the agonist dopamine and W6.48, suggesting a reorientation of W6.48 on agonist binding, consistent with proposed “rotamer switch” models. Interestingly, no comparable cation–π interaction was found at the aligning residue in the M2 receptor.

Item Type:Article
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URLURL TypeDescription CentralArticle
Lester, Henry A.0000-0002-5470-5255
Dougherty, Dennis A.0000-0003-1464-2461
Additional Information:©2009 by the National Academy of Sciences. Edited by Laura L. Kiessling, University of Wisconsin, Madison, WI, and approved May 1, 2009 (received for review March 24, 2009). Published online before print July 6, 2009, doi: 10.1073/pnas.0903260106 We thank C. Doupnik for advice and plasmids and A. Kovoor for helpful discussions. This work was supported by National Institutes of Health Grants GM 081662 and NS011756. Author contributions: M.M.T., K.S.B., H.A.L., and D.A.D. designed research; M.M.T. and K.S.B. performed research; M.M.T., K.S.B., H.A.L., and D.A.D. analyzed data; and M.M.T., K.S.B., and D.A.D. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at
Funding AgencyGrant Number
NIHGM 081662
Subject Keywords:D2 receptor; fluorination; membrane protein
Issue or Number:29
PubMed Central ID:PMC2715518
Record Number:CaltechAUTHORS:20090901-141204665
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15532
Deposited By: George Porter
Deposited On:08 Sep 2009 19:19
Last Modified:08 Nov 2021 23:20

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