Structural determinants of A(3) adenosine receptor activation: nucleoside ligands at the agonist/antagonist boundary.

Mutagenesis of the human A(3) adenosine receptor (AR) suggested that certain amino acid residues contributed differently to ligand binding and activation processes. Here we demonstrated that various adenosine modifications, including adenine substitution and ribose ring constraints, also contributed differentially to these processes. The ligand effects on cyclic AMP production in intact CHO cells expressing the A(3)AR and in receptor binding were compared.