Figure 1
From: Physical constraints on the establishment of intracellular spatial gradients in bacteria
A phosphorylation gradient can be produced by fast asymmetric source and sink activities. A) Schematic of localization of source and sink. B) Mathematical modeling of the spatial asymmetry in phosphorylated response regulator for different source and sink rates. A substantial gradient is obtained only when the phosphorylation rate σ k and dephosphorylation rate σ p are faster than the inverse of the time scale required for diffusion across the cell, 1/τ D = 2D/L2. We model the cell in 1D with length L = 2 μm and poles of extent r p  = 0.25 μm. The diffusion constant is D = 2 μm2/s. (Inset) The ratio of R∼P between the two poles ηis virtually independent of the source rate σ. k