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. Author manuscript; available in PMC: 2006 Dec 4.

Published in final edited form as: Nat Rev Mol Cell Biol. 2006 Mar;7(3):165–176. doi: 10.1038/nrm1838

FIG. 3 — Spatial segregation of two opposing enzymes in a protein-modification cycle generates intracellular gradients. Kinases localize to (A) supra-molecular structures (sphere) or (B) the cell membrane, whereas phosphatases are homogeneously distributed in the cytoplasm. The concentration gradients are shown by colour intensity. C. Stationary phosphorylation levels c_p decline with the distance d from the cell membrane toward the centre[Brown, 1999 #61 (see panel B). The steepness of the gradient (reciprocal of the characteristic length) is determined by the parameter α(α² = k_p/D is the ratio of the phosphatase activity k_p and the protein diffusivity D, BOX 3).

FIG. 3 — Spatial segregation of two opposing enzymes in a protein-modification cycle generates intracellular gradients. Kinases localize to (A) supra-molecular structures (sphere) or (B) the cell membrane, whereas phosphatases are homogeneously distributed in the cytoplasm. The concentration gradients are shown by colour intensity. C. Stationary phosphorylation levels c_p decline with the distance d from the cell membrane toward the centre[Brown, 1999 #61 (see panel B). The steepness of the gradient (reciprocal of the characteristic length) is determined by the parameter α(α² = k_p/D is the ratio of the phosphatase activity k_p and the protein diffusivity D, BOX 3).