Fig. 1. Schematic representation of the plasmid constructs used in this study. To generate a potential expressed substrate for PKA we added two features to the C-terminus of ß₂AR. The first was to add a myristylation sequence to target the truncated protein to the membranes, where ß₂AR normally resides. We also included a hemagglutinin (HA) antigenic epitope to facilitate detection by immunoblotting. In addition to myr-HA-ß₂AR-C, we also constructed myr-HA-ß₂AR-C/PKA^- (substituting both Ser³⁴⁵ and Ser³⁴⁶ with Ala), myr-HA-ß₂AR-C/GRK^- [substituting all 11 GRK sites with either Ala or Gly, as described previously (Hausdorff et al., 1989)] and myr-HA-ß₂AR-C/PKA^-&GRK^- (containing neither PKA nor GRK sites). myr, myristylation; HA, hemagglutinin tag.