MUTATIONAL ANALYSIS OF THE ANGIOTENSIN-II TYPE-2 RECEPTOR - CONTRIBUTION OF CONSERVED EXTRACELLULAR AMINO-ACIDS

While much work has been done examining the ligand-binding characteris tics of the AT(1) receptor, very little attention has been focused on the AT(2) receptor. Both receptors bind angiotensin II (AngII) with id entical affinities, but share only 34% homology. Although it is tempti ng to assume that conserved residues between the two subtypes are resp onsible for the binding of AngII, there is little data to support this view. To determine the commonalities in ligand binding of the AT(1) a nd AT(2) receptors, we have chosen several conserved extracellular ami no acids which have been shown to be important in AngII binding [1,2] to the AT(1) receptor for mutational studies of the AT(2) receptor. Sp ecifically, we have mutated tyrosine(108) in extracellular loop 1 (ECL 1), arginine(182) in ECL2, and aspartate(297) in ECL3 of the AT(2) rec eptor in order to determine their contribution to AngII binding. In th e AT(2) receptor, mutation of tyrosine(108) to an alanine resulted in a receptor with wild-type binding for AngII, while mutation of either arginine(182) or aspartate(297) drastically impaired AngII binding (>1 00 nM). These results demonstrate both similarities as well as clear d ifferences between receptor subtypes in the contributions to AngII bin ding of several conserved extracellular amino acid residues. (C) 1997 Elsevier Science B.V.