The first transmembrane domain (TM1) of β2-subunit binds to the transmembrane domain S1 of α-subunit in BK potassium channels

► The regionsof BK β-subunit required for association with α-subunit are yet unknown. ► We found that some regions of the β2-subunitare dispensable for this process. ► Weshow that TM1 of the β2-subunit physically binds to the S1 of the α-subunit.