Each channel has two transmembrane domains and two nucleotide binding domains. ATP binding to both nucleotide binding domains causes changes these domains to associate, further causing changes that open up the ion pore. When ATP is hydrolyzed, the nucleotide binding domains dissociate again and the pore closes. Pathology Cystic fibrosis is caused by mutations in the CFTR gene on chromosome 7, the most common mutation being deltaF508 (a deletion of a codon coding for phenylalanine, which occupies the 508th amino acid position in the normal CFTR polypeptide). Any of these mutations can prevent the proper folding of the protein and induce its subsequent degradation, resulting in decreased numbers of chloride channels in the body. This causes the buildup of mucus in the body and chronic infections. Other chloride channels and families GABAA Glycine Receptor Calcium-activated chloride channel Anion-conducting channelrhodopsin References Further reading External links - CLC chloride channels Membrane proteins Transmembrane transporters Integral membrane proteins Protein domains