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. 2010 Oct;136(4):367–387. doi: 10.1085/jgp.201010430

Figure 7.

Figure 7.

C276A prevents the PCMBS-mediated increase in channel activation. Ca2+ concentration response experiments and variance analysis were undertaken to determine whether PCMBS increases C276A channel activation in the same manner observed for the WT channel. (A) Representative macroscopic current record from an inside-out patch expressing KCa3.1 C276A channels. All experiments were performed using the Ca2+ concentraiton response protocol described in Fig. 3. (B) Plot of normalized 〈I〉 current against the corresponding Ca2+i for KCa3.1 C276A (■) and KCa3.1 C276A+PCMBS (▾). All analyses were performed according to the protocol described in Fig. 3 to give averages: KCa3.1 C276A (solid line, n = 18), EC50 = 460 ± 27 nM and h = 1.7 ± 0.04, and KCa3.1 C276A+PCMBS (dashed line, n = 9), EC50 = 485 ± 68 nM and h = 1.6 ± 0.04. Error bars represent SEM. (C) Variance analysis as described in Fig. 2 to determine Po(max), N, and i in the absence of PCMBS: Po(max) = 0.67, n = 488, and i = 3.3 pA. PCMBS did not increase steady-state current in KCa3.1 C276A; therefore, to obtain an estimate of Po(PCMBS), Po had to be extrapolated using the equation where Po = Po(max)(I/I(max)) and Po(PCMBS) = 0.63. Analysis of multiple patches (n = 6) indicates that PCMBS did not increase Po(max) (0.68 ± 0.05 in the absence of PCMBS and 0.59 ± 0.05 in PCMBS).