(A) Gatekeeper is located near RS3, and in some cases these residues are in contact. In the figure, gatekeeper of the protein kinase IGF1R (PDB ID: 3qqu [28]) is shown with orange surface and RS3 with blue surface. (B) Distribution of gatekeeper residues according to their RS3 residue (in parenthesis) represented in pie charts. (C) Correlation matrix of RS3 and gatekeeper residues. The unique RS3-gatekeeper combination containing kinases are labelled.