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. 2009 Nov 19;285(5):3103–3113. doi: 10.1074/jbc.M109.053249

FIGURE 7.

FIGURE 7.

Effects of valine substitution. NLC curves for each mutant group were constructed from mean fit parameters, and all values are reported as mean ± S.E. A, valine obviates the shift induced by serine replacement at residue 395. C395V prestin exhibited z and V½ values that were consistent with WT but had reduced charge density (p < 0.05). For C395V (n = 15), V½ = −70.4 ± 2.6 mV, z = 0.73 ± 0.02, and Qmax/Clin = 6.50 ± 0.73 fC/pF. B, valine substitution is well tolerated in the hydrophobic core of TMD 4. NLC curves for each prestin mutant show V½ and z values consistent with WT, except for C196V, which was significantly different for both (p < 0.05). For WT, V½ = −78.6 ± 3.6 mV and z = 0.67 ± 0.01 (n = 21); for C192S, V½ = −68.4 ± 1.8 mV and z = 0.72 ± 0.01 (n = 16); for C192V, V½ = −69.8 ± 1.8 mV and z = 0.75 ± 0.02 (n = 10); for C196S, V½ = −89.5 ± 2.0 mV and z = 0.74 ± 0.03 (n = 15); for C196V, V½ = −102.2 ± 1.8 mV and z = 0.76 ± 0.02 (n = 14); for C192S/C196S, V½ = −68.3 ± 2.8 mV and z = 0.70 ± 0.02 (n = 7). C, any substitution of cysteine by serine in TMD 4 reduced charge density (p < 0.05), whereas valine replacement resulted in WT function. Charge densities (fC/pF) for each of the mutants of B are displayed in C. Bars that do not share a common letter are significantly different (p < 0.05). For WT, Qmax/Clin = 18.27 ± 1.89 fC/pF (n = 21); for C196V, Qmax/Clin = 15.57 ± 1.88 fC/pF (n = 14); for C192V, Qmax/Clin = 11.48 ± 2.83 fC/pF (n = 10); for C192S/C196S, Qmax/Clin = 7.37 ± 0.81 fC/pF (n = 7); for C196S, Qmax/Clin = 7.05 ± 0.95 fC/pF (n = 15); for C192S, Qmax/Clin = 5.65 ± 0.40 fC/pF (n = 16). D, similar to the results for TMD 4, valine substitution in TMD 10 provides WT charge density. C415V prestin has normal charge density (Qmax/Clin), hyperpolarized V½ (p < 0.05), and normal z compared with WT. C415V (n = 15): V½ = 107.2 ± 2.7 mV; z = 0.68 ± 0.01; Qmax/Clin = 15.23 ± 2.43 fC/pF.