Figure 2.

PPi opens WT-CFTR in a Mg-dependent manner. (A) WT-CFTR channels were exposed to a nucleotide-free solution for 3 min before they were treated with different combinations of [PPi] and [Mg²⁺]. Raising PPi concentration fails to further increase channel activity if [Mg²⁺] was not increased simultaneously. (B) Current elicited by PPi at different concentrations was normalized to the original ATP current. (Red line) The PPi solution was supplement with the same concentration of Mg²⁺. (Blue line) [Mg²⁺] in the PPi solution was fixed at 2 mM.