kfRr(L Second reduction LT p K ffA(l) t eff1(L) kef(L) pt eff3 2 LT LT 3 additional assumption CheB only demetylates phosphorylated receptors experimental backup not possible to directly measure if Cheb demethylate only active receptors rate of methylation drops immediately after addition of ligand indicates that CheB works on active receptors
T2 LT2 T3 LT3 T2p LT2p T3p LT3p keff1(L) keff2(L) keff3(L) keff4(L) keff3(L) kpt kpt Second reduction additional assumption: - CheB only demetylates phosphorylated receptors experimental backup: - not possible to directly measure if CheB demethylates only active receptors - rate of methylation drops immediately after addition of ligand indicates that CheB works on active receptors 11
Third reduction In p 工T p effi additional assumption [CheR]<< [receptors], methylation operates at saturation eff2 in IS independent of receptor concentrations) r 3 LT experimental backup Michaelis constant of Cher binding < [receptors] so R
T3 LT3 T3p LT3p keff2(L) rin keff4 rin kpt Third reduction additional assumption: - [CheR]<< [receptors], methylation operates at saturation (rin is independent of receptor concentrations) experimental backup: - Michaelis constant of CheR binding << [receptors] so Rtot ~ Rbnd ok 12
Fourth reduction In p 工T p effi additional assumption demethylation is identical for bound and unbound receptors, So eff2 kefta is independent of L r 3 LT experimental backup kinetics of demethylation almost independent of level of methylation and ligand binding
T3 LT3 T3p LT3p keff2(L) rin keff4 rin kpt Fourth reduction additional assumption: - demethylation is identical for bound and unbound receptors, so keff4 is independent of L. experimental backup: - kinetics of demethylation almost independent of level of methylation and ligand binding. ok 13