![Figure 1. Current records of homotetrameric recombinant type 3 InsP3R channels in membrane patches excised from nuclei isolated from DT40-KO-r-InsP3R-3 cells. (A) Activation by InsP3 of channels in a cyto-out nuclear membrane patch. Concentrations of InsP3 and free Ca2+ in the perfusion solution on the cytoplasmic side of the channel are indicated by color bars at top. Vapp = 30 mV. Channels opened only in the presence of cytoplasmic InsP3. Gray arrowheads indicate some of the occasions when one of the active channels entered a conductance substate. In this and subsequent current traces, black arrows indicate the membrane current levels when all InsP3R channels in the membrane patch were closed. (B) Single InsP3R-3 channel current records observed in different lum-out nuclear patches in symmetric 140 mM KCl and 3 µM [Ca2+]f. Pipette solution contained 10 µM InsP3. Vapp = 40 mV. Gray arrowheads indicate when the channels entered different conductance substates with different conductance values. (C) Representative I-Vapp plot for a single InsP3R-3 channel in the same experimental conditions as in B. Vapp was ramped from −25 to 15 mV in 1 s. 20 ramps were analyzed. Data points selected for Iopen and Iclosed are plotted in green and pink, respectively. Green and red lines represent linear fits to Iopen and Iclosed data points, respectively.](https://cdn.rupress.org/rup/content_public/journal/jgp/136/6/10.1085_jgp.201010513/5/jgp_201010513_rgb_fig1.jpeg?Expires=1771774887&Signature=Bi2A8Bl4IPkqEkhY2IE32Dzr4q8SMOzJNMjFaDOAlEUeYJC~s5IdkweUPtbatFIwhjo5yUt4zicyR9l~bWetgnwSzFHI2JTrx3NKNMkMexuX7h7QVgBcymPp9c0w-kzl0wbUKoR0LuqqPPBuYG6XCiiytYqPWK44cMMCZo6PXaAMz~5R2u~NLMfxeQLHlrYp~DXbnchN49bWVCYj58clyIcLTD9gGLO0KiTO9us-LqMxB1mSuNcY8J2hSnbBOBzY9drHumk8GXvNeVTrxb93xcSkah0BdnAvaDFU4PnnFpcArOiCom~MktoniNB1wXJ7m4GgdKqS7PrRS3qwcU~ZgQ__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Current records of homotetrameric recombinant type 3 InsP3R channels in membrane patches excised from nuclei isolated from DT40-KO-r-InsP3R-3 cells. (A) Activation by InsP3 of channels in a cyto-out nuclear membrane patch. Concentrations of InsP3 and free Ca2+ in the perfusion solution on the cytoplasmic side of the channel are indicated by color bars at top. Vapp = 30 mV. Channels opened only in the presence of cytoplasmic InsP3. Gray arrowheads indicate some of the occasions when one of the active channels entered a conductance substate. In this and subsequent current traces, black arrows indicate the membrane current levels when all InsP3R channels in the membrane patch were closed. (B) Single InsP3R-3 channel current records observed in different lum-out nuclear patches in symmetric 140 mM KCl and 3 µM [Ca2+]f. Pipette solution contained 10 µM InsP3. Vapp = 40 mV. Gray arrowheads indicate when the channels entered different conductance substates with different conductance values. (C) Representative I-Vapp plot for a single InsP3R-3 channel in the same experimental conditions as in B. Vapp was ramped from −25 to 15 mV in 1 s. 20 ramps were analyzed. Data points selected for Iopen and Iclosed are plotted in green and pink, respectively. Green and red lines represent linear fits to Iopen and Iclosed data points, respectively.
