Figure 1
From: Extrapolating microdomain Ca2+ dynamics using BK channels as a Ca2+ sensor
The biphasic currents of BK-type channels elicited by flash photolysis of caged-calcium.
(A) Trace shows the current from a whole-cell patch from a HEK293 cell transfected with cDNA encoding mouse Slo1 α-subunits. The current was stimulated firstly by a voltage step from a 100-ms holding potential of −60 mV to the 600-ms testing voltage of +30 mV and then by a 0.2-ms UV pulse (pink line) at 500 ms as indicated at the bottom. The measured [Ca2+]i in blue triangle is placed at the top. The boxed current elicited by flash showed a biphasic activation with a fast on-time constant τf = ~0.2 ms, a fast off-time constant τf-off = ~2.4 ms and a slow time constant τs = ~10 ms. The proportion of fast and slow components is respectively defined as Rf = h1/h and Rs = h2/h as indicated. (B) The representative currents, evoked by flash, of mSlo1 and its five mutants as indicated. (C) The fast proportion Rf of the above currents as shown in (B). The Rf is 60 ± 7.56% (n = 10) for mSlo1, 75.84 ± 7.68% (n = 10) for D362A/D367A, 25.96 ± 6.20% (n = 10) for 5D5N, 0.0% (n = 10) for D362A/D367A/5D5N and 89.35 ± 6.57% (n = 10) for D369G. Statistical significance for all data was determined using One Way ANOVA (*P < 0.05, **P < 0.01, ***P < 0.001).
