The p.Cys169Tyr variant of connexin 26 is not a polymorphism.
Bottom Line: We have analyzed the effect of this mutation using a combination of confocal immunofluorescence microscopy and molecular dynamics simulations.At the molecular level, this effect can be accounted for by disruption of the disulfide bridge that Cys169 forms with Cys64 in the wild-type structure (Cx26WT).Our results elucidate the molecular pathogenesis of hereditary hearing loss due to the connexin mutation and facilitate the understanding of its role in both healthy and affected individuals.
Affiliation: Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, 35131 Padova, Italy.Show MeSH
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Mentions: To corroborate the hypothesis that the p.Cys169Tyr mutation prevents the formation of Cx26 intercellular channels, we used molecular dynamics simulations (22–24). In the extracellular region of the Cx26WT protein, Cys169 forms a (strong covalent) disulfide bond with Cys64, which keeps the distance between the two sulfur atoms at 2.05 A. In the Cx26C169Y protein, the p.Cys169Tyr substitution makes the formation of this bond impossible and produces an alteration in the distance between residues 64 and 169 (Fig. 3). The distance between the α carbons of these residues, averaged over the six connexin subunits of the connexon, was derived from 100 ns of equilibrium molecular dynamics and plotted as a function time in Figure 4 (left). Figure 4 (right) shows frequency histograms of distance distributions for the wild-type and the mutant connexon. The p.Cys169Tyr substitution modifies the mean value and the variance of these distributions, from 5.9 ± 0.2 Å for the wild-type to 6.6 ± 0.1 Å for the mutant. Although small, this difference (i) is statistically significant (P < 0.0001, Student's t-test) and (ii) alters the structure of the hemichannel in the extracellular region (particularly the E2 loop). Visual inspection of the molecular dynamics trajectories revealed a remarkable deformation affecting two of the proteins of the hexameric assembly. Albeit less pronounced, deformations were detectable also in the remaining four connexins.Figure 3.
Affiliation: Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, 35131 Padova, Italy.