Table 1.

List of parameters in reaction–diffusion equations, their reference value in the simulations, and their physical meaning in the model. Unless indicated, the values were estimated or adjusted to match experimental observations as mentioned in the main text.

Variable	Reference Value	Description
$D_{\mathrm{T}}$	0.02 μm2/s	Diffusion coefficient of Cdc42-GTP from [33]
$D_{\mathrm{D}}$	0.2 μm2/s	Diffusion coefficient of Cdc42-GDP from [33]
$D_{{\mathrm{GAP}}_{\mathrm{I}}}$	0.03 μm2/s	Diffusion coefficient of GAPI, estimated
$D_{{\mathrm{GAP}}_{\mathrm{II}}}^{\mathrm{fast}}$	0.0625 μm2/s	Diffusion coefficient of fast GAPII, estimated
$D_{{\mathrm{GAP}}_{\mathrm{II}}}^{\mathrm{slow}}$	0.005 μm2/s	Diffusion coefficient of slow GAPII, estimated
$k_1^n$	0.000625/s	Spontaneous rate Cdc42-GTP hydrolysis, adjusted
$k_2^n$	0.00325 μm2/s	Rate constant of GAPI-mediated Cdc42-GTP hydrolysis, adjusted
$k_3^n$	0.00125 μm2/s	Rate constant of fast GAPII-mediated Cdc42-GTP hydrolysis, adjusted
$k_4^n$	250/s	Rate constant of Cdc42-GTP-mediated GAPI recruitment, adjusted
$k_5^n$	0.03/s	Rate constant of Cdc42-GTP-mediated GAPII recruitment, adjusted
$k_6^n$	2/s	Rate of fast GAPII conversion to slow form, adjusted
$k_7^n$	0.025 μm2/s	Cdc42-GTP-mediated conversion of slow to fast GAPII, adjusted
$k_8^n$	0.0005 μm2/s	Rate constant of slow GAPII-mediated Cdc42-GTP hydrolysis, adjusted
$k_{\mathrm{sat}}$	600/μm2	Saturating concentration of GAPI negative feedback, adjusted
$k_0^p$	0.0025 μm2/s	Rate constant of GEF-mediated Cdc42-GDP activations, adjusted
$k_1^p$	0.5 μm3	Linear rate constant of GEF recruitment to Cdc42-GTP, adjusted
$k_2^p$	0.1 μm5	Quadratic rate constant of GEF recruitment to Cdc42-GTP, adjusted
$E_c{}^{\mathrm{tot}}$	250	Total pool of GEFs, estimated
$j_{\mathrm{D}}^p$	2.4/s/μm2	Flux of Cdc42-GDP from cytoplasm to membrane, estimated
$r_{\mathrm{T}}$	0.005/s	Rate of Cdc42-GTP dissociation from membrane from [33]
$r_{\mathrm{D}}$	0.03/s	Rate of Cdc42-GDP dissociation from membrane from [33]
$r_{{\mathrm{GAP}}_{\mathrm{I}}}$	0.01/s	Rate of GAPI dissociation from membrane, adjusted
$r_{{\mathrm{GAP}}_{\mathrm{II}}}^{\mathrm{fast}}$	0.0125/s	Rate of fast GAPII dissociation from membrane, adjusted
$r_{{\mathrm{GAP}}_{\mathrm{II}}}^{\mathrm{slow}}$	0.0025/s	Rate of slow GAPII dissociation from membrane, adjusted
$r_{\mathrm{noise}}$	0.0021/s	Rate of random Cdc42-GDP conversion to Cdc42-GTP, adjusted
$\lambda$	2.5 μm	GEF activation scale at cell tips, estimated
L	8 μm	Cell length