Table 1.

Model parameters used in this study

ParameterUnit, symbolValueReferences
GEF, Sec3, v-SNARE, Cdc42 copy numbers1,000 (bem1Δ: 350), 377, 1,000, 3,000Saccharomyces Genome Database; M&M
Maximal number of endocytic coats/early endocytic proteins (simplified endocytic pathway)200/1,000Saccharomyces Genome Database; M&M; Agrawal et al., 2010
Diffusion constant, Cdc42, GEF complex, and early endocytic patchesμm2s−1, Dm0.036M&M; Marco et al., 2007; Slaughter et al., 2009
Diffusion constant, v-SNARESμm2s−1, Dmslow0.0025Valdez-Taubas and Pelham, 2003; Marco et al., 2007
Radius of the cellμm, Rc3Layton et al., 2011; Savage et al., 2012
GEF complex membrane-binding rates−1, k11From Bem1 FRAP (Layton et al., 2011; Savage et al., 2012)
GEF complex unbinding rates−1, k−11//
Bimolecular and trimolecular GEF complex–mediated Cdc42 activation rateμM−1s−1, k2, k30.16, 0.63Layton et al., 2011; Savage et al., 2012
Cdc42 inactivation rates−1, k−20.35//
Trimolecular complex dissociation rates−1, k−410//
Trimolecular complex assembly rates (from cytosol and membrane)μM−1s−1, k4, k710, 10//
Cdc42-GDP binding and unbinding ratess−1, kb, ku10, 0.02, rdi1Δ: 0.5, 0.001M&M
Actin cables detachment rates−1, kdet10M&M; Yang and Pon, 2002
Cdc42-mediated cable nucleation rates−1, knuc0.1//
Coefficient for negative feedback on cable nucleationunitless, β1.5//
Cable growth durations, dnuc6//
Coefficient for negative feedback on cable detachmentunitless, βtot2M&M; Marco et al., 2007; Slaughter et al., 2009
Vesicle secretion rate from the internal buffer to actin cabless−1, Kex3, LatA treated cells: 0Layton et al., 2011; Savage et al., 2012
Rate of exocyst complex assembly per Sec3 proteins−1, kexocyst10Liu et al., 2005; Domanska et al., 2009; Karatekin et al., 2010
Rate of SNARE complex assemblys−1, ksnare64//
Fusion rates−1, kfus40//
Maximal number of Cdc42-GTP per exocytic vesicle8From SV2 protein count in rat brain synaptic vesicles (Mutch et al., 2011)
Maximal number of Cdc42-GDP per exocytic vesicle8//
Maximal number of v-SNARES per vesicle8In vitro study (Liu et al., 2005; Domanska et al., 2009; Karatekin et al., 2010)
Maximal number of endocytic coat proteins per exocytic vesicle1 complete coatM&M
Rate of early endocytic patch transition to coat recruitment phase (complete model)s−1, kcoatWT: 0.0103, sla2Δ,sla1Δ/bbc1Δ: 0.0025, LatA-treated cells: 0M&M
Duration of coat recruitment phases, dcoat5//
Rate of coated patch transition to Cdc42/v-SNARE loading phases−1, kgrowthWT: 1, sla2Δ: 0.25//
Duration of Cdc42/v-SNARE loading phase and actin-driven growths, dgrowth10This study (Fig. 2 B); Liu et al., 2009; Carroll et al., 2012
Endocytic scission rates−1, kscWT: 10, rvsΔ: 0.1, sla1Δ/bbc1Δ: 0.5Scission is not rate limiting in WT cells (Liu et al., 2009; Carroll et al., 2012). We chose ksc >> 1
Cdc42-GDP endocytic loading rates−1, kload0.4Chosen to allow continuous cycling of cargo proteins
Cdc42-GTP endocytic loading rates−1, Embedded Image0.4//
v-SNARE endocytic loading rates−1, kloadv40//
  • // indicates same as previous row.