FIGURE 3.
Cell surface expression of loss-of-function slide helix mutant channels. A and B, CosM6 cells were transfected with various Kir6.2 slide helix mutants that result in loss of function in Rb+ efflux assays (identified in Fig. 2). In addition, the Kir6.2[H259R] (coexpressed with WT SUR1) and SUR1[R1419H] (coexpressed with WT Kir6.2) mutations, both reported previously to disrupt trafficking of KATP channels, were tested. Labeling of surface-exposed protein was done using sulfo-NHS-SS-biotin followed by isolation of biotinylated protein using streptavidin-coated beads. Proteins in the cell lysate or the purified surface fraction were separated by SDS-PAGE and detected with a monoclonal anti-SUR1 antibody (NeuroMAb). Similar data were obtained in three separate experiments.