Model for analysis of fraction of GTPase at the membrane.

<p>A. Model for lumped variables and rates. The term in the dotted box includes effector bound GTPases. The dashed arrows represent the GDI mediated membrane cycling of GTPases. B–F. Fraction of GTPase at the membrane free from GDI as <i>ρ_Eq</i> ranges from 0 to 10. The upper contour corresponds to 9% fraction at the membrane, while the lowest line represents 89%. Each pair of neighboring lines is 10% apart in membrane fraction. When <i>ρ_Eq</i> = 0, all membrane bound GTPase is free from GDI (<i>r0</i> = <i>r0_f</i>). The total fraction of GTPase at the membrane <i>r0</i> is represented by the dashed lines when <i>ρ_Eq</i>>0.