Membrane localization of Dr-VSP. (A) Representative current traces of Kir2.1 recorded from HEK293T cells coexpressed with mCherry fused Dr-VSP WT in pcDNA3.1 (lower) with whole-cell patch configuration. The pulse protocol used to estimate VSP activity (upper) consisted of a 50-ms step pulse to −120 mV (test pulse) and a 300-ms depolarization pulse to 100 mV. This protocol was repeated 21 times without an interval. The holding potential was −60 mV. (B) The phosphatase activities of Dr-VSP^mChe. Data are the mean ± SD from seven cells, and each symbol shows the data from each cell. Two cells showed no phosphatase activity and were excluded from the analysis. Values in parentheses indicate the numbers of cells. (C) Representative confocal microscope images of Dr-VSP^mChe (left) and a chimeric protein (Ci-VSP [M1-G103] + Dr-VSP [Q44-P511] [CiDr-VSP^mChe]; right) expressed in HEK293T cells. Bright field images (BF) and fluorescence images of mCherry are shown. Scale bar, 20 µm. (D) Topologies of Dr-VSP^mChe (left) and CiDr-VSP^mChe (right).