Fig. 8. Macroscopic currents through mutant Kir7.1M125R channels in Xenopus oocytes. A, Sequence alignment of the core region between the pore helix and the M2 (inner) helix of Kir7.1, Kir2.1, and Kv1.3 channels, as suggested by Doyle et al. (1998), show the residues mutated in this study.Boxed in white are residues conserved in all Kir channels; boxed in black are residues identical between Kir7.1 and mostly present in Kv channels.B, Whole-cell voltage-clamp responses of oocytes expressing mutant Kir7.1M125R channels to 500 msec voltage steps between −80 and −140 mV from a holding potential ofVh = 0 mV in 2, 25, and 96 mm[K+]e, as indicated.C, Current–voltage (I–V) relationship of Kir7.1M125R currents measured at the end of the 500 msec voltage pulse in 0 (•), 1 (⋄), 2 (▪), 5 (▵), 10 (▴), 50 (♦), and 96 mm (■) extracellular K+.