Xenbase Image ID: 159288

Figure 4. No asymmetry in the timing of motions can be detected at the level of the coupling helices.(A, F, K) Inward unitary currents of the cut-ΔR(D1370N) CFTR background construct, and of channels bearing mutations at position 172 (A), 961 (F), or 1068 (K), in the same background. Letters to the left of the traces indicate the amino acid present in the target position; the native residue is marked by red. Currents were recorded at −80 mV, in symmetrical 140 mM Cl-; dashes on the left mark zero-current level. (B–D, G-I) and (L–N), Mean burst (B, G, L, τb) and interburst (C, H, M, τib) durations and open probabilities (D, I, N, Po) of the constructs in A, F, and K, respectively. Red horizontal lines highlight the respective control values of the background construct which is identified by the red letter representing the native target residue. All data are shown as mean ± SEM (n = 3–8 for data in (B–D), n = 4–15 for data in G-I, n = 4–7 for data in L-N). (E, J, O) Brønsted plots for position 172 (E), 961 (J), and 1068 (O). Red symbol and letter identifies the background construct. Solid lines are linear regression fits with slope Φ indicated.Figure 4—figure supplement 1. Burst analysis of single-channel recordings for position 172 mutants.(A, F) Inward currents of single cut-ΔR(D1370N) channels bearing mutation L172Y (A) or L172E (F) in 10 mM MgATP (green bars). (B–C, G–H), Closed (B, G) and open (C, H) dwell-time histograms (Sigworth and Sine, 1987) constructed from the events list of the records in (A, F); lower binning limit is 12 ms. Solid red lines are maximum likelihood fits of the dwell-times by a double- and a single-exponential distribution, respectively, with time constants (τ(1, 2)) and fractional amplitudes (a1, a2) printed in the panels. Dotted black lines in panels (B, G) depict the two components of the fit; vertical blue line marks the burst delimiter (tcrit) calculated using the method of (Magleby and Pallotta, 1983). (D–E, I–J) Dwell-time histograms of reconstructed interburst (D, I) and burst (E, J) events following suppression of closed events shorter than tcrit. Solid red lines in (D, I) replot the longer component of the double-exponential fits in (B, G). Solid red lines in (E, J) are maximum likelihood fits of the burst durations by single-exponential distributions (τ, time constant). A single long interburst event in F marked by an asterisk was omitted from the analysis. Image published in: Sorum B et al. (2017) © 2017, Sorum et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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