Redox reagents and divalent cations alter the kinetics of cystic fibrosis transmembrane conductance regulator channel gating

Gating of the cystic fibrosis Cl- channel requires hydrolysis of ATP by its nucleotide binding folds, but how this process controls the kinetics of ch annel gating is poorly understood. In the present work we show that the kin etics of channel gating and presumably the rate of ATP hydrolysis depends o n the species of divalent cation present and the oxidation state of the pro tein. With Ca2+ as the dominant divalent cation instead of Mg2+, the open b urst duration of the channel is increased approximately 20-fold, and this c hange is reversible upon washout of Ca2+. In contrast, "soft" divalent cati ons such as Cd2+ interact covalently with cystic fibrosis transmembrane con ductance regulator (CFTR). These metals decrease both opening and closing r ates of the channel, and the effects are not reversed by washout. Oxidation of CFTR channels with a variety of oxidants resulted in a similar slowing of channel gating, In contrast, reducing agents had the opposite effect, in creasing both opening and closing rates of the channel. In cell-attached pa tches, CFTR channels exhibit both oxidized and reduced types of gating, rai sing the possibility that regulation of the redox state of the channel may be a physiological mode of control of CFTR channel activity.