A residue in the middle of the M2-M3 loop of the β4 subunit specifically affects gating of neuronal nicotinic receptors

An aspartate residue in the M2-M3 loop of neuronal nicotinic receptor alpha(7) subunits is a major determinant of the channel functional response. This residue is conserved in most beta(4) subunits, e.g. human and rat, but not in others, e.g. bovine, We have used these differences to examine the mechanism by which this residue alters the functional properties of alpha(3)beta(4) receptors, Having ruled out an effect on the macroscopic binding ability of the agonist, the level of receptor expression, or the single channel conductance, the results suggest that receptors lacking that residue have a deficient coupling between binding and gating, (C) 1998 Federation of European Biochemical Societies.