Abstract
Rearrangement of transmembrane domains (TMs) 3 and 5 after agonist binding is necessary for stabilization of the active state of class A G protein-coupled receptors (GPCRs). Using site-directed mutagenesis and functional assays, we provide the first evidence that the TAS(I/V) sequence motif at positions 3.37 to 3.40, highly conserved in aminergic receptors, plays a key role in the activation of the histamine H1 receptor. By combining these data with structural information from X-ray crystallography and computational modeling, we suggest that Thr3.37 interacts with TM5, stabilizing the inactive state of the receptor, whereas the hydrophobic side chain at position 3.40, highly conserved in the whole class A GPCR family, facilitates the reorientation of TM5. We propose that the structural change of TM5 during the process of GPCR activation involves a local Pro5.50-induced unwinding of the helix, acting as a hinge, and the highly conserved hydrophobic Ile3.40 side chain, acting as a pivot.
Footnotes
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The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This work was supported by the Ministerio de Educación y Ciencia [Grant SAF2010-22198-C02-02]; the Instituto de Salud Carlos III [Grant RD07/0067/0008]; and the Ministerio de Educación y Ciencia through the Ramon y Cajal program (to X.D.).
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.066068.
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ABBREVIATIONS:
- GPCR
- G protein-coupled receptor
- H1R
- H1 receptor
- WT
- wild type
- TM
- transmembrane
- t
- trans
- g+
- gauche+
- g−
- gauche−
- NF-κB
- nuclear factor κB.
- Received May 5, 2010.
- Accepted November 16, 2010.
- Copyright © 2011 The American Society for Pharmacology and Experimental Therapeutics
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