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. 2024 Oct 9;18(1):2402749. doi: 10.1080/19336950.2024.2402749

Figure 11.

This figure shows the on- and off rates for TPrA in KcvNTS and KcvS for the respective wild type and channels that are mutated on positions 77 and/or 78. The data are divided into six panels to avoid overcrowding. Panels A and C show that exchanging Serine and Glycine at position 77 switches the blocking phenotype between the two channels. Panels B and C show that the effect of mutations on position 78, either as single-point mutations or combined with mutations at position 77, is very complex.

Block by TPrA. Influence of the residues at positions 77 and 78 on the rate constants of (a, b, c) blocker binding kon = kOB/[TPrA] and (d,e,f) release (kBO = koff) in different mutants of KcvNTS and of KcvS. Lines show the wild-type data (KcvNTS: continuous, KcvS: dashed), the symbols indicate the residue at locations 77: G = filled, S = open for the mutants (a,d) S77G and G77S (b,e) F78A and (c,f) the double mutants. “pooled:” wt data averaged over TPrA concentration from 0.05 – 5 mM (KcvNTS) and 0.1 – 1 mM (KcvS), data for KcvNTS S77G F78A averaged over 0.1 & 1 mM. All other blocker concentrations are indicated in the legends. All data points: mean ± sd of at least three experiments each. Because of the decrease of the signal with higher negative voltages, rate constants could not be determined from fitting amplitude histograms for voltages more negative than −80 mV or −60 mV for all mutants and KcvS.