Long-Range Effect of Mutations on Specific Conformational Changes in the Extracellular Loop 2 of Angiotensin II Type 1 Receptor

摘要: The topology of the second extracellular loop (ECL2) and its interaction with ligands is unique in each G protein-coupled receptor. When orthosteric ligand pocket located transmembrane (TM) domain occupied, ligand-specific conformational changes occur ECL2. In more than 90% receptors, ECL2 tethered to third TM helix via a disulfide bond. Therefore, understanding extent which conformations are coupled useful. To investigate this, we examined angiotensin II type 1 receptor (AT1R) by introducing mutations distant sites that alter activation state equilibrium AT1R. Differential accessibility reporter cysteines introduced at four conformation-sensitive these mutants was measured. Binding agonist (AngII) inverse losartan wild-type AT1R changed cysteines, pattern consistent "lid" Without stimulation, gain function mutant N111G assumed lid conformation similar AngII-bound presence agonists, inactive contrast, AngII did not induce loss D281A mutant, reduced binding affinity this mutant. However, induced [Sar(1),Gln(2),Ile(8)] AngII, specific analog binds better AngII. These results provide evidence for emerging paradigm coupling facilitated long range interactions on same