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The two-state dimer receptor model. A general model for receptor dimers Supplementary material. Rafael Franco, Vicent Casadó, Josefa Mallol, Carla Ferrada, Sergi Ferré, Kjell Fuxe, Antoni Cortés, Francisco Ciruela, Carmen Lluis and Enric I. Canela Correspondence address: Enric I. Canela
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The two-state dimer receptor model. A general model for receptor dimersSupplementary material Rafael Franco, Vicent Casadó, Josefa Mallol, Carla Ferrada, Sergi Ferré, Kjell Fuxe, Antoni Cortés, Francisco Ciruela, Carmen Lluis and Enric I. Canela Correspondence address: Enric I. Canela Dept. Bioquimica i Biologia Molecular Universitat de Barcelona Av. Diagonal, 645. 08028 Barcelona. Spain ecanela@ub.edu
Scheme of the model DIMER OPERATING UNIT Inactive Vacant K mK A+A+(RR) A+A(RR) A(RR)A a L L ba L a K mbK A+A+(RR)* A+A(RR)* A(RR)*A Constitutive Occupied Active
Constants List of the equilibrium constants for the two-state dimer model & In this symmetric dimer model [A(RR)] refers to the concentration of dimer with A bound, i.e irrespective of whether A is bound to one site or the other.
Ligand binding I. Functions The ligand binding function The saturation function is a 2:2 function
Ligand binding II. Cooperativity analysis Reference saturation function Saturation function It corresponds to a theoretical noncooperative binding of A to a dimer K is the average association constant
Ligand binding III. Cooperativity analysis If Positive cooperativity If Negative cooperativity If Noncooperativity. Occurs when
Ligand binding IV. Fitting data to the model Rearranging and defining c1 and c2 where being . • c2 gives an idea of the affinity • positive cooperativity occurs when c1 < 2·[A]50 • negative cooperativity occurs when c1 > 2·[A]50 • c1 = 2·[A]50 gives noncooperativity
Scheme of the model for two competing ligands A + A + B+B+(R2) A + A + B+B+(R2)* A + B+(R2)*B A + B+(R2)B (R2)B2 (R2)*B2 q M fw M L q L qw L ad K a K M f M A + B+(R2)*A A + B+(R2)A K g K (R2)*AB (R2)AB qd M a L aqd/g L bm K g M mK (R2)A2 (R2)*A2 ba L
Constants for competing agent List of the equilibrium constants for the two-state dimer model & In this symmetric dimer model [B(RR)] refers to the concentration of dimer with B bound, i.e irrespective of whether B is bound to one site or the other.
Competition experiments I. Function The ligand binding function Being A the initial bound ligand and B the competing ligand
Competition experiments II. Fitting data to the model defining c3, c4 and c5
Competition experiments III. Fitting data to the model Substituting and rearranging
Competition experiments IV. Fitting data to the model Simplifying when A binding is noncooperative or