Fig. 5.

CFTR residues that contribute to ion selectivity and/or ion conduction. (A) Residues shown to contribute to ion selectivity or conduction in the literature are mapped onto the three-dimensional structure of CFTR. The pore is shown as a blue surface. Chloride is shown as a green sphere. Residues in the inner and outer vestibules are pink. Residues that directly coordinate chloride at S_filter are yellow. Residues of the second coordination sphere of S_filter are cyan. (B) Closeup views of the extracellular opening (Upper) and cytosolic opening (Lower) of CFTR’s pore. The pore is outlined as a blue surface. (C) Chloride coordination at the S_cen chloride-binding site in wild-type EcClC (Upper, Protein Data Bank 1OTS) (80) and at the S_filter chloride-binding site in CFTR (Lower).