Figure 1.

Single-channel conductance and ROMK2/IRK1 chimeras. (A) ROMK2/IRK1 chimeras. Parts of ROMK2 are white, and parts of IRK1 are shaded. Chimera C13 has the entire COOH terminus, probably including the last part of the second transmembrane domain (M2), from IRK1, and the rest of the channel from ROMK2. Other chimeras have progressively smaller portions of the COOH terminus from IRK1. (B) Inward current traces measured in the cell-attached configuration with a cell potential of −100 mV with respect to the pipette. The dotted lines indicate the closed state, with upward deflections indicating channel openings. (C) I–V relationships. Data represent means ± SEM for at least three different patches. A minimum of 15 transitions at each voltage were measured to obtain values for each patch. Slope conductances measured between −60 and −140 mV were ROMK2, 43 pS; C13, 31 pS; C132, 18 pS; C133, 37 pS; C133a, 38 pS; C134, 51 pS; and C135, 46 pS.