FIGURE 1.

β₅c/β₆c hairpin within the model of the three-dimensional structure of human CFTR. A, global view of the model of human CFTR in an outward-facing conformation (open channel) in which the β₅c/β₆c hairpin (in pink) discussed here is circled. B, focus on the β₅c/β₆c hairpin and on the amino acids, which are mutated in this study. His⁶²⁰, Glu⁶²¹, Gly⁶²², and Ser⁶²³ are the four residues (i to i+3) of the β turn, with His⁶²⁰ and Ser⁶²³ making two hydrogen bonds between their NH and O atoms (dashed green lines). Neighbors of His⁶²⁰ (Ser⁴⁵⁹) and Glu⁶²¹ (Gln¹³³⁰) are also shown. C, focus on the Gly⁶²⁸ position, which was mutated in the three-dimensional model in an arginine residue (G628R), highlighting the steric clashes (orange lines), which would be associated with this mutation.