BKIP-1 and SLO-1 coimmunoprecipitated from transfected HEK293 cells. A, Diagrams of putative membrane topologies of SLO-1 and BKIP-1. The numbers indicate the positions in which truncation or deletion was made in the experiments shown in B and C. B, BKIP-1 coimmunoprecipitated with full-length SLO-1 or SLO-1Δ371–1140 but not SLO-1Δ1–370. C, BKIP-1Δ1–13 but not BKIP-1Δ30–42 or BKIP-1Δ51–60 coimmunoprecipitated with SLO-1. In both B and C, BKIP-1 and its variants were tagged with HA, whereas SLO-1 and its variants were tagged with Myc. Immunoprecipitation (IP) and immunoblot (IB) were performed with Myc and HA antibodies. All specific bands are indicated by their relative molecular sizes, and nonspecific bands are indicated by arrows.