Functional effects of tryptophan substitutions in the M4 transmembrane domain olthe nicotinic acetylcholine receptor

The structural basis of function in Cys-loop receptors

“…The α-helical nature of these regions, which was originally inferred from hydropathy plots (Noda et al 1982), was verified in the nAChR by photolabelling (Blanton & Cohen, 1994), two-dimensional 1 H-NMR spectroscopy (Lugovskoy et al 1998), Fourier transform infrared (FTIR) spectroscopy (Baenziger & Methot, 1995; Corbin et al 1998; Görne-Tschelnokow et al 1994; Methot et al 1994) and mutagenesis (e.g. Tamamizu et al 2000). The best available structural information comes from 4 Å resolution cryo-electron microscopy images of the nAChR (Miyazawa et al 2003); higher-resolution structures from related prokaryotic receptors have been solved, but it is not yet clear how representative these are of vertebrate Cys-loop receptors (Bocquet et al 2009; Hilf & Dutzler, 2008; Nury et al 2009).…”

“…Given the location and apparent roles of M3 and M4, it is surprising that mutations can have significant effects on receptor function, but such mutations cause changes in both the whole-cell current (Cruz-Martin et al 2001; Guzman et al 2003; Lasalde et al 1996; Williams & Akabas, 1999; Wu et al 2010) and single-channel kinetics of nAChRs and 5-HT 3 Rs (Bouzat et al 2000, 2002; Corradi et al 2009; De Rosa et al 2002; Lee et al 1994; Navedo et al 2004; Ortiz-Miranda et al 1997; Tamamizu et al 1999, 2000; Wang et al 1999). The effect of these mutations can be additive both in terms of the contribution from each subunit (Bouzat et al 1998; De Rosa et al 2002) and within the same α-helix (Lasalde et al 1996), although this observation is not supported by all studies (Cruz-Martin et al 2001).…”