Figure 5.

In vitro phosphorylation of peptide based on the C terminus of TXA₂ receptors by G kinase. Kinase reactions contained 8 nM purified G kinase, [γ-³²P]ATP, and recombinant GST protein (G), the GST-TXA₂ receptor third intracytoplasmic loop (iL3), or the GST-TXA₂ receptor tail sequence fusion protein corresponding to the α or β isoforms of the TXA₂ receptor (α and β, respectively). Proteins were quantitated by Bradford assay and on Coomassie-stained gels, and the same input concentrations of protein were used for the various peptides. Left and right panels represent two different experiments. Reactions were resolved on 10% SDS/PAGE gels to generate the autoradiographs shown. (Right) Dark arrowhead denotes the TXA₂ α carboxyl-terminal fusion protein; open arrowhead denotes the TXA₂ receptor β carboxyl-terminal fusion protein. One of three similar experiments is shown in each case.