Lysates were prepared from bulk-selected HeLa cells that stably express wild type Cx26, Cx30, or both Cx30 and Cx26 (Cx26/Cx30) or one of the Cx26 mutants as indicated (Cx26 mutation/Cx30), co-culture of stable Cx26 cells and Cx30 cells (Cx26+Cx30), as well as HeLa cells that were transiently transfected to express both Cx26 and Cx43 (Cx26/Cx43). The lysates were immunoprecipitated with a mouse monoclonal antibody against Cx26 (M Cx26), and the bound fractions or the unbound fraction were probed (upper panels) with a rabbit antiserum against Cx30 (Rb Cx30) or Cx43 (Rb Cx43), then reprobed (lower panels) with a rabbit antiserum against Cx26 (Rb Cx26). Note that M Cx26 co-immunoprecipitated Cx30 (double arrowhead), but not Cx43 (triple arrowheads), which is present in the unbound fraction (UB). Reprobing the blot reveals Cx26 in the appropriate samples (single arrowheads); the signal for Cx30 remains because the blot was not stripped before reprobing. Size markers (in kDa) are shown.