Oscillations in an external signaling module of kinase X by the positive feedback of the MAPK cascade S2. (A) Dynamics of X-P with and without the positive feedback loop when rate of phosphorylation of X (Xphos ) = rate of dephopshorylation of X (Xdephos ). Here Xphos = Xdephhos = 0.1. (B) Dynamics of phosphorylated X (X-P) when Xphos > Xdephos. The Xphos = 0.5 and X dephos = 0.1. (C) Dynamics of X-P when Xdephos.> Xphos. The Xphos = 0.1 and X dephos = 0.5. (D) Dynamics of X-P when Xdephos.> > Xphos. The Xphos = 0.1 and X dephos = 5. In the simulations, total concentration of X was 100 nM (arbitrary). The units of Xphos and Xdephhos is nM.sec-1.