Fig. 3: Functional characterization of SthK with PIP2 binding site mutations.
From: PIP2 inhibits pore opening of the cyclic nucleotide-gated channel SthK
Representative single-channel recordings for (a) SthK R120A, (b) SthK R124A, and (c) SthK R120A/R124A in the presence of 300 µM cAMP reconstituted into 3:1 DOPC:POPG (top traces) and 3:1 DOPC:POPG + 5 % PIP2 (bottom traces). Recordings at −100 mV and +100 mV are shown. Average Po ± s.d. of (d) SthK R120A, (e) SthK R124A and (f) SthK R120A/R124A at different voltages without PIP2 (squares) and in the presence of 5 % PIP2 (circles). The number of independent repeats, n, is indicated for each voltage in the plots. Individual data points are shown in grey. g Comparison of initial Tl+ flux rates of the different SthK variants. Averaged values ± SEM (n = 3 independent repeats) of measurements with different lipid compositions are normalized to the rate without PIP2 of the respective variant. Individual data points are shown in grey. h Normalized Po of single channel recordings at + 100 mV of different SthK variants in bilayers with or without 5 % PIP2. Averaged values ± s.d. are shown (number of independent repeats, n, for each condition is shown in the corresponding bars) as well as individual data points (grey). Statistical significance was assessed with a two-tailed unpaired t-test with a confidence level of 95 % resulting in P = 4 × 10−8 for WT SthK and P = 5 × 10−8 for SthK R120A. *** P < 0.001.
