Parameter	Description	Value	Justification
ka	Unitless base activation rate	0.01 [51]	Order-of-magnitude from [38]
kb	Overall activation rate	10 s–1	Order-of-magnitude from [38]
kc	Deactivation rate	10 s–1	Order-of-magnitude from [38]
Ka	Positive feedback threshold for actin promoter concentration	1 μm –2	Order-of-magnitude from [38]
Da	Actin promoter diffusion coefficient	0.8 μm 2/s	Typical membrane-bound protein diffusion coefficient [52]
$D_m^0$	Myosin diffusion coefficient at zero actin concentration	2 μm 2/s	Chosen in [12]
KD	Myosin diffusion threshold, $D_m=D_m^0/(1+{\rho }_a/K_D)$	0.5 μm –2[53]	Chosen in [12]
$N_a^{\text{tot}}$	Total amount of actin promoter	485* [54]	Roughly rescaled by cell size from value chosen in [12] proportional to cell area
${\rho }_m^0$	Initial density of myosin	0.3 μm –2	Chosen such that myosin stress corresponds to that estimated in [14]