4bvn

Publication Abstract from PubMed

The beta1-adrenoceptor (beta1AR) 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 beta1AR mutant bound to the weak partial agonist cyanopindolol to 2.1 A resolution. High-quality crystals (100 mum 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 beta1AR and the adenosine A2A receptor (rmsd of 0.3 A), despite an overall rmsd of 2.4 A for all Calpha atoms and only 23% amino acid identity in the transmembrane regions. The affinity of agonist binding and nanobody Nb80 binding to beta1AR is unaffected by Na+ ions, but the stability of the receptor is decreased by 7.5 degrees C 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 beta1AR by 5-10 degrees C. The data suggest that the intramembrane Na+ and associated water network stabilise the ligand-free state of beta1AR, but still permits the receptor to form the activated state which involves the collapse of the Na+ binding pocket on agonist binding.

The 2.1 A Resolution Structure of Cyanopindolol-Bound beta1-Adrenoceptor Identifies an Intramembrane Na+ Ion that Stabilises the Ligand-Free Receptor.,Miller-Gallacher JL, Nehme R, Warne T, Edwards PC, Schertler GF, Leslie AG, Tate CG PLoS One. 2014 Mar 24;9(3):e92727. doi: 10.1371/journal.pone.0092727. eCollection, 2014. PMID:24663151^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.