Figure 7.

ATP sensitivity of the R310C and R314C mutants (linked to GFP) coexpressed with SUR1. (A) ATP sensitivity in an inside-out patch with R301C+SUR1 in the presence of 200 μM MgADP to slow channel rundown. Inward currents were progressively suppressed by increasing ATP concentrations, with the IC₅₀ for channel inhibition near 200 μM. Note the inhibition of channel rundown in the presence of ATP. Upon removal of ATP, there was a potent recovery of channel activity followed by prominent rundown. (B) In the absence of ADP, channel rundown was more pronounced, however, ATP could still stop rundown, but after removal of ATP channel rundown was almost complete. The IC₅₀ for channel inhibition by ATP was close to 40 μM in this case. (C) Plot of channel ATP sensitivity for R301C+SUR1 with (•) and without (▾) 200 μM MgADP. In this case, a fit of the data points yielded k = 205 μM and n = 1.14 (•; n = 5) and k = 38 μM and n = 1.2 (▾; n = 3).