Myasthenic nicotinic receptor mutant interpreted in terms of the allosteric model.
An extended Monod-Wyman-Changeux allosteric-type model is applied to human muscle nicotinic acetylcholine receptors expressed in HEK cells, for both the normal form and the high-affinity human myasthenic mutant, epsilon T264P. The model is based on a concerted transition between the basal (resting) B state and the active (open-channel) A state, with the equilibrium in the absence of ligand determined by the allosteric constant, L0 = [B0]/[A0]. For wild-type receptors the model with L0 = 9 x 10(8) provides a satisfactory representation of published patch-clamp recordings that yields a distribution of open-channel dwell times with a single peak at 0.7 ms. For the epsilon T264P mutant, the model with L0 = 100 accounts for the trimodal distribution reported for open-channel dwell times, with peaks at 0.15, 3.8 and 60 ms that correspond to non-, mono- and bi-liganded receptors, respectively. Possible applications of the allosteric model to other myasthenic mutants are considered.
Edelstein
S J
SJ
Département de biochimie, université de Genève, Switzerland.
Schaad
O
O
Changeux
J P
JP
D000495:Allosteric Site; D006801:Humans; D015640:Ion Channel Gating; D008954:Models, Biological; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011950:Receptors, Cholinergic / Q000235:genetics / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*
D009124:Muscle Proteins; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic