+ATT ATT flagellar +cH3- 器 motor MCPs MCPs CW -CH3 ATP ATP ADP B P Figure 1 of Spiro, P A, J. S. Parkinson and H. G. othmer A model of excitation and adaptation in bacterial chemotaxis Proc Nat/ Acad SciUSA 94, no 14 (Jul 8, 1997): 7263-8 Copyright(1997) National Academy of Sciences, U.S.A key player: Tar-CheA-CheW complex
6 Figure 1 of Spiro, P. A., J. S. Parkinson, and H. G. Othmer. Proc Natl Acad Sci U S A 94, no. 14 (Jul 8, 1997): 7263-8. "A model of excitation and adaptation in bacterial chemotaxis." key player: Tar-CheA-CheW complex Copyright (1997) National Academy of Sciences, U. S. A
Phosphorylation Methylation Bindingintermediate gand 午T SLOW-T2 4 fast 3p·FLT4 Y B Figure 2 of Spiro, P. A, J. S. Parkinson, and H. G. Othmer A model of excitation and adaptation in bacterial chemotaxis Proc Nat/ Acad SciUSA94, no 14 ( Jul 8, 1997): 7263-8 Copyright (1997) National Academy of Sciences, U.S.A
fast slow intermediate Copyright (1997) National Academy of Sciences, U. S. A. Figure 2 of Spiro, P. A., J. S. Parkinson, and H. G. Othmer. Proc Natl Acad Sci U S A 94, no. 14 (Jul 8, 1997): 7263-8. "A model of excitation and adaptation in bacterial chemotaxis
First reduction ff4 p p LT LT Kfrr(l) f effl (L) Kff(L) f2 KffA (L e 3 LT LT 3 keffi(L) ff [3] in steady state C≡ [2]+[3] k,=(1-c)k eff1 (L)+ak pnos eff2
T2 LT2 T3 LT3 T2p LT2p T3p LT3p keff1(L) keff2(L) keff3(L) keff4(L) keff3(L) keff4(L) kpt kpt First reduction 1-α α [2] [3] [3] α + in steady state: ≡ 8 (L) eff2 (L) αk eff1 (1 α)k phos k = − +
perfect adaptation for small L K/k ef128 safe zone perfect adaptation for large L K/ eff18 0 6 8 10 K. L fine-tune: net phoshorylation rate and keff and keff2 so that a falls in safe zone
safe zone net phosphorylated rate perfect adaptation for large L perfect adaptation for small L 9 fine-tune: net phoshorylation rate and keff1 and keff2 so that α falls in safe zone
no safe zone never perfect adaptation K/ eff2 8 K/K eff18 0 10
net phosphorylated rate no safe zone never perfect adaptation 10