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Table 2 Binding parameters of interactions of soluble receptors with immobilized ligands.

From: Receptor oligomerization and beyond: a case study in bone morphogenetic proteins

Ligand Type I receptor (analyte) Type II receptor (analyte)
  ActR-I ActR-IB BMPR-IA BMPR-IB ActR-II ActR-IIB BMPR-II
  Mean SD Mean Mean SD Mean SD Mean SD Mean SD mean SD
BMP-2              
k on × 10-4 [M-1s-1] NB   NB 3.9 ± 0.63 2.3 ± 0.56 NE   NE   NE  
k off × 103 [s-1] NB   NB 1.9 ± 0.47 8.0 ± 1.38 > 100   > 100   > 100  
K D (kin) [nM] NB   NB 48 ± 19.6 350 ± 146 NE   NE   NE  
K D (eq) [nM] NB   NB NE   NE   3800 ± 608 3100 ± 527 13000 ± 2470
GDF-5              
k on × 10-4 [M-1s-1] NB   NB 0.5 ± 0.162 0.3 ± 0.09 NE   NE   NE  
k off × 103 [s-1] NB   NB 17 ± 1.90 1.0 ± 0.124 > 100   > 100   > 100  
K D (kin) [nM] NB   NB 3300 ± 1439 300 ± 123 NE   NE   NE  
K D (eq) [nM] NB   NB NE   NE   22000 ± 2420 4700 ± 658 60000 ± 9600
BMP-7              
k on × 10-4 [M-1s-1] NE   NB 0.3 ± 0.05 3.1 ± 0.38 NE   NE   NE  
k off × 103 [s-1] NE   NB 5.4 ± 0.70 23 ± 5.84 > 100   > 100   > 100  
K D (kin) [nM] NE   NB 1900 ± 589 750 ± 283 NE   NE   NE  
K D (eq) [nM] 58000 ± 29140 NB NE   NE   880 ± 61.6 2500 ± 300 9100 ± 1365
Activin-A              
k on × 10-4 [M-1s-1] NB   NB NB   NB   30 ± 3.30 14 ± 2.38 10 ± 1.23
k off × 103 [s-1] NB   NB NB   NB   44 ± 10.6 9.6 ± 2.78 76 ± 19.3
K D (kin) [nM] NB   NB NB   NB   180 ± 63.0 88 ± 40.5 890 ± 335
K D (eq) [nM] NB   NB NB   NB   NE   NE   NE  
  1. The data obtained from the interaction soluble type I receptor ectodomains (ECDs) with the immobilized ligands were fitted to the 1:1 Langmuir binding model and the K D (kin) (bold) calculated as k off (× 103 s-1)/k on (× 10-4 M-1 s-1). Due to the fast kinetics of the interaction between type II receptors as analyte and the immobilized ligands BMP2, BMP7 and GDF5, the data could only be fitted by equilibrium dose response K D (eq). The dissociation rate constants (k off) of these interactions are >100 (× 103 s-1). All data represent mean values of three repeated measurements using at least six different analyte concentrations.
  2. ActR = activin receptor; BMP(R) = bone morphogenic protein (receptor); GDF = growth and differentiation factor; NB = no binding above background detected; NE = could not be evaluated; SD = standard deviation.