Mapping the residues of a kinase superfamily that most frequently form pockets highlights two regions. A Provar analysis of 93 members of the phosphorylase/kinase superfamily mapped onto a representative structure [PDB:2R3I]. (A) Residues which are very frequently pocket-lining (light red - 86% of structures - to dark red - 96%) cluster around the active site region. The active site is indicated by ATP in yellow, superimposed from an ATP-bound structure [PDB:2PVF]. (B) A second region in which residues are very frequently involved in pocket formation is found on the opposite side of the kinase from the active-site. (C) Some of the conserved features highlighted in (B) may be important in mediating protein-protein interactions. For example, it is known that one member of this superfamily, Abl kinase, is regulated via an interaction at this site with its own SH3 domain (superimposed SH3 domain from [PDB:2FO0] blue ribbon).