English: Representative P-site binding simulation showing competition between active sites. Animation showing a trajectory from a representative P-site binding simulation in the first of three views (see also Videos S2 and S3). Pseudo-atoms of the receiver and activator receptor monomers are represented as beads colored in shades of pink and blue, respectively, with bound growth factor molecules in dark blue. In both monomers the catalytic Asp-813 residue is colored cyan and the tyrosines of all P-sites are colored green. The 1840 trajectory images represent 1 nsec intervals during the complete 1.8 µsec simulation. This first animation shows the motion of the dimeric EGFR from a view through the plane of the membrane. The simulation begins with P-site-1148A of the receiver monomer binding to the active site of activator (see close-up in Video S3, at ∼5 sec), which is followed by its displacement by P-site-1045A (at ∼30 sec), continues with the displacement of P-site-1045A by P-site-1068A (at ∼50 sec), and ends with the binding of P-site-992A to the catalytic site of the receiver (last frame, see also Video S2). The simulation suggests that the binding of P-sites to the active site of the activator monomer can delay the interaction of another P-site with the true catalytic site in the receiver monomer.