XB-IMG-123964
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Figure 2. Coexpression of Slo3 with β4 does not appreciably increase single channel conductance or effective Po.In A, traces show openings from a patch with a single Slo3+β4 channel at +150 mV with pH 8.5 (filtering at 10 kHz). In B, a total amplitude histogram of all digitized current values from a 995 ms record of Slo3+β4 single channel activity is plotted, showing a substantial number of current values between the closed level (0 pA) and the largest open level (∼18 pA). Histograms were fit with a 3-component Gaussian function to estimate the fraction and amplitude of the closed level, the smaller current level (gS) and the larger current level (gL). In C, the gS fraction of all open current levels is plotted as a function of voltage (3–5 patches). In D, the mean conductance for gS, gL, and the overall mean is plotted as a function of voltage. In E, σ2 is plotted as a function of mean current level for current recorded from a single patch at 5 different voltages. For each voltage, a set of 100 repeated steps to the nominal voltage was used to activate currents from which σ2 and mean current, I, were determined for each time point in the average. The σ2/I relationships at multiple voltages were fit simultaneously by σ2(I,V) = g*V*I - I2/N with best fit values indicated by the solid lines, yielding g = 82.7±1.5 pS and N = 1284.5±73.6 channels. In F, the mean conductance estimated from single channel measurements at +150 mV (n = 5) and the single channel conductance estimated from σ2/I estimates (n = 6) are compared, along with previous estimates for Slo3 alone (dotted line). In G, estimates of Po for Slo3+β4 patches at pH 8.5 obtained either from σ2/I estimates (black circles, n = 3–6) or from the mean single channel current estimate (red diamond, n = 5) are plotted as a function of voltage and compared to previous estimates from Slo3 (dotted line). Image published in: Yang CT et al. (2009) Yang 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 |