CFTR and cystic fibrosis: To characterize the features of the fold contributing to the function of the CFTR polypeptide sequence, we measured at physiological temperature (37 °C) the trafficking and chloride conductance properties of 64 most frequent CFTR missense variants in the CF population that are dispersed along the entire polypeptide sequence dictating the organization of the structural fold2–4 (Fig. 1b).