TABLE 1

Allosteric model binding parameters for the interaction between the orthosteric antagonist [3H]NMS and each of three prototypical allosteric modulators at various M2 mAChR mutants.

Values represent the mean ± S.E.M. from three to eight experiments performed in triplicate. pKB is the negative logarithm of the equilibrium dissociation constant. Bmax is the maximal density of binding sites. Log α is the logarithm of the cooperativity factor governing the allosteric interaction between the modulator and [3H]NMS.

Orthosteric Ligand [3H]NMS Allosteric Modulator
M2 Receptor Construct Alcuronium Gallamine C7/3-phth
pKBBmax pKB Log α pKB Log α pKB Log α
pmol/mg
M2-WT 9.20 ± 0.20 2.30 ± 0.30 5.96 ± 0.03 0.61 ± 0.03 5.95 ± 0.05 −1.55 ± 0.06 6.56 ± 0.03 −0.83 ± 0.03
M2-EDGE 9.16 ± 0.36 1.00 ± 0.16* 5.56 ± 0.05* 0.64 ± 0.09 5.25 ± 0.05* −1.26 ± 0.07 5.90 ± 0.04* −0.63 ± 0.03*
M2-YT 8.80 ± 0.12 2.93 ± 0.96 4.64 ± 0.07* 0.10 ± 0.02* 4.99 ± 0.06* −1.54 ± 0.08 5.49 ± 0.04* −0.97 ± 0.04
M2-EDGE-YT 8.77 ± 0.28 3.15 ± 0.15 4.56 ± 0.05* −0.18 ± 0.03* 4.43 ± 0.06* −1.05 ± 0.07* 5.19 ± 0.04* −0.84 ± 0.04
  • * Significantly different (P < 0.05) from the wild-type receptor as determined by one-way analysis of variance.