XB-IMG-122646
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Figure 8. High Ca2+ sensitivity in dSlo1 is not related to the low affinity metal binding site. (A) Steady-state G-V relations of mSlo1 and dSlo1 at 89 μM [Ca2+]i and indicated [Mg2+]i. Boltzmann fits (smooth curves) gave following parameters: mSlo1, for 0 [Mg2+]i, V1/2 = −2.8 mV, z = 1.2, for 10 mM [Mg2+]i, V1/2 = −73.8 mV, z = 1.1; dSlo1, for 0 [Mg2+]i, V1/2 = −2.9 mV, z = 1.1, for 10 mM [Mg2+]i, V1/2 = −69.2 mV, z = 0.94. (B) Steady-state G-V relations of the E413R mutant dSlo1 channel. Boltzmann fits (solid curves) gave the following: E413R, for 5.7 μM [Ca2+]i, V1/2 = 163 mV, z = 1.1, for 89 μM [Ca2+]i, 0 [Mg2+]i, V1/2 = −24.6 mV, z = 0.95, for 89 μM [Ca2+]i, 10 mM [Mg2+]i, V1/2 = −46.7 mV, z = 0.87. Dotted lines are G-V relations for dSlo1 at 5.7 μM [Ca2+]i and 89 μM [Ca2+]i, 0 [Mg2+]i. (C) Free energy provided by Mg2+ binding for channel activation in mSlo1, dSlo1, and E413R dSlo1 when [Mg2+]i changes from 0 to 10 mM, measured at [Ca2+]i of 89 μM. (D) Free energy provided by Ca2+ binding for channel activation in WT and E413R dSlo1 when [Ca2+]i changes from 5.7 to 89 μM. Image published in: Krishnamoorthy G et al. (2005) Copyright © 2005, The Rockefeller University Press. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View |