Figure 5. Fluorescence signal indicating... | Rockefeller University Press

Figure 5.

$Figure 5. Fluorescence signal indicating conformational changes of S4. (A) Fluorescence response to depolarizing pulses from −90 mV to voltages between−120 and 100 mV and 180 mV for ShakerIR-A359C and ShakerIR-A359C-I384N/F484G, respectively, for a duration of 100 ms. Channels are fluorescently labeled with tetramethyl-rhodamine maleimide at position A359C on top of the S4. (B) Time constants of exponential fits of the onset of the fluorescence signal obtained in A. (C) Comparison of fluorescence signals for saturating pulses of ShakerIR-A359C (V1/2 = −37.5 mV), ShakerIR-A359C-I384N (V1/2 = −55.4 mV), and ShakerIR-A359C-F484G (V1/2 = −56.8 mV). (D) QV of ShakerIR-W434F from a holding potential (HP) of −90 mV to a prepulse of 0 mV for variable duration (0–50 ms) followed by a series of pulses of 30 to −160 mV in steps of 10 mV. The QV curves were fitted to a sum of two Boltzmann curves. (middle) The shift of the V1/2 of the two Boltzmann distributions as a function of the duration of the depolarizing prepulse is shown. The shifts were fitted to single exponentials with time constants of τ = 4.0 and 8.8 ms for more positive and more negative ones, respectively. (right) The fraction of the QV0 Boltzmann as a function of the duration of the depolarizing prepulse is shown. (B and D) Data shown are mean ± SD.$

Fluorescence signal indicating conformational changes of S4. (A) Fluorescence response to depolarizing pulses from −90 mV to voltages between−120 and 100 mV and 180 mV for ShakerIR-A359C and ShakerIR-A359C-I384N/F484G, respectively, for a duration of 100 ms. Channels are fluorescently labeled with tetramethyl-rhodamine maleimide at position A359C on top of the S4. (B) Time constants of exponential fits of the onset of the fluorescence signal obtained in A. (C) Comparison of fluorescence signals for saturating pulses of ShakerIR-A359C (V_1/2 = −37.5 mV), ShakerIR-A359C-I384N (V_1/2 = −55.4 mV), and ShakerIR-A359C-F484G (V_1/2 = −56.8 mV). (D) QV of ShakerIR-W434F from a holding potential (HP) of −90 mV to a prepulse of 0 mV for variable duration (0–50 ms) followed by a series of pulses of 30 to −160 mV in steps of 10 mV. The QV curves were fitted to a sum of two Boltzmann curves. (middle) The shift of the V_1/2 of the two Boltzmann distributions as a function of the duration of the depolarizing prepulse is shown. The shifts were fitted to single exponentials with time constants of τ = 4.0 and 8.8 ms for more positive and more negative ones, respectively. (right) The fraction of the QV₀ Boltzmann as a function of the duration of the depolarizing prepulse is shown. (B and D) Data shown are mean ± SD.