Differential equations of the reduced MAPK model.

c1 and c2 are the rate and Michaelis constant for RasGDP activation by the Shc-Grb-Sos (ShcGS) complex, respectively; c3 is the rate for RasGTP to be converted to RasGDP; c4 is the rate for RasGTP to convert Raf from an inactive to an active form (Raf*); c5 is the rate for RasGTP to convert Raf* to Raf; c6 is the rate for Raf* to convert Mek from an inactive to an active form (Mek*); c7 is the rate for Mek* to be converted to Mek; c8 and c9 are the rate and Michaelis constant, respectively, for Mek* to convert Erk from an inactive form to an active form (Erk*); c10 and c11 are the rate and Michaelis constants, respectively, for Erk* to be converted to Erk. Finally, c12 is the rate for the ShcGS complex to be inhibited by Erk* (See simulated curves in Figure S3).