Figure 1.

SOS binding interactions with allosteric and substrate Ras proteins. An illustrative cartoon depicts SOS domains from the N- to C-terminus (left to right): H (purple), PH (orange), DH (magenta), REM (green), and Cdc25 (blue) domains. The H domain interacts directly with a membrane that helps SOS to anchor on a membrane. The DH domain functions with the H and PH domains to control access of the allosteric Ras in the REM site. The REM domain that binds the allosteric Ras (red) controls the catalytic function of the catalytic Cdc25 domain that binds the substrate Ras (orange)