Peptide coverage of the human PAR4 construct by MS and H/D exchange map of the apo and thrombin-activated states of human PAR4. (A) Green line, the extracellular side of the PAR4 sequence; red line, the intracellular domain of PAR4; blue, the transmembrane domains; black, the C-terminal 1D4 tag. The black underline indicates the peptide coverage in H₂O, D₂O apo state, and D₂O thrombin-activated state. Only the peptides that are shown in all 3 states and that have a significant score with a P value <.05 were selected and further analyzed. (B-E) Side view of PAR4 in apo and thrombin-activated states. (F-G) Top and bottom views of PAR4 in apo and thrombin-activated states, respectively. In all panels, the apo state of PAR4 is on the left and the thrombin-activated state is on the right. The PAR4 homology model is color-coded on the basis of the H/D exchange level: dark blue for 0% to <2%, light blue for 2% to <10%, cyan for 10% to <18%, cadet blue for 18% to <26%, green for 26% to <34%, light green for 34% to <42%, yellow for 42% to <50%, orange for 5% to <58%, and red for 58% to 66%. Undefined regions are gray.