Download MendeleyThe 2.1 A Resolution Structure of Cyanopindolol-Bound Beta1- Adrenoceptor Identifies an Intramembrane Na+ Ion that Stabilises the Ligand-Free Receptor.
Miller-Gallacher, J.L., Nehme, R., Warne, T., Edwards, P.C., Schertler, G.F.X., Leslie, A.G.W., Tate, C.G.(2014) PLoS One 9: 92727
- PubMed: 24663151
- DOI: https://doi.org/10.1371/journal.pone.0092727
- Primary Citation of Related Structures:
4BVN - PubMed Abstract:
The ¦Â1-adrenoceptor (¦Â1AR) is a G protein-coupled receptor (GPCR) that is activated by the endogenous agonists adrenaline and noradrenaline. We have determined the structure of an ultra-thermostable ¦Â1AR mutant bound to the weak partial agonist cyanopindolol to 2.1 ? resolution. High-quality crystals (100 ¦Ìm plates) were grown in lipidic cubic phase without the assistance of a T4 lysozyme or BRIL fusion in cytoplasmic loop 3, which is commonly employed for GPCR crystallisation. An intramembrane Na+ ion was identified co-ordinated to Asp872.50, Ser1283.39 and 3 water molecules, which is part of a more extensive network of water molecules in a cavity formed between transmembrane helices 1, 2, 3, 6 and 7. Remarkably, this water network and Na+ ion is highly conserved between ¦Â1AR and the adenosine A2A receptor (rmsd of 0.3 ?), despite an overall rmsd of 2.4 ? for all C¦Á atoms and only 23% amino acid identity in the transmembrane regions. The affinity of agonist binding and nanobody Nb80 binding to ¦Â1AR is unaffected by Na+ ions, but the stability of the receptor is decreased by 7.5¡ãC in the absence of Na+. Mutation of amino acid side chains that are involved in the co-ordination of either Na+ or water molecules in the network decreases the stability of ¦Â1AR by 5-10¡ãC. The data suggest that the intramembrane Na+ and associated water network stabilise the ligand-free state of ¦Â1AR, but still permits the receptor to form the activated state which involves the collapse of the Na+ binding pocket on agonist binding.
Organizational Affiliation:
Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom.
