FIGURE 2.

Functional assay of Kir7.1-HA cloned from the choroid plexus of a Kir7.1-HA knock-in mouse. (A) Cartoon showing a topological model of the Kir7.1 protein in the membrane and the site of the insertion of the HA-epitope with the chromatogram with of the cDNA sequencing. In capital letters is the amino acid sequence deduced from the nucleotide sequence. Large red letters identify the G plus HA tag (G-YPYDVPDYA) inserted in frame between residues 90 and 91 of the native protein. (B–E) Whole-cell currents obtained from a HEK-293 cell after transfection of the Kir7.1-HA cDNA. The cell was held at the stated V_h and square voltage pulses were given that took the membrane potential from –160 to 80 mV in 20 mV steps. The cell contained 145 mM K⁺ and the medium was switched from one containing 5 mM K⁺ (B) to 145 mM K⁺ (C), 145 mM Rb⁺ (D) and finally to 145 mM Rb⁺ with 1 mM Ba²⁺ (E). In (F), current–voltage relations for the currents at the end of the pulses in (B–E) are shown. (G) Is a comparison of Rb⁺ currents at –160 mV measured in cells transfected with untagged Kir7.1 channel with those of Kir7.1-HA channel (means ± SD and individual points, n = 8 and 9 respectively).