CFTR

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CFTR regulates ion concentration in extracellular fluid due to its role as a plasma membrane Cl channel in epithelial cells.[1]

CFTR is the name commonly given to the gene responsible for the production of the Cystic Fibrosis Transmembrane Regulator protein. This gene, when mutated, can cause cystic fibrosis, although it is recessive, whether the mutations are identical or not. So far, over 1500 mutations of the CFTR gene have been discovered, the most common being the ∆F508 mutation, sometimes in as few as one individual. Some of the other more common mutations include; ΔF508 G542X G551D N1303K and W1282X. In the ∆F508 mutation a phenylalanine residue at amino acid 508 has been deleted and so the channel is no longer functional [2]. This mutation is a class II mutation where abnormal processing occurs in the endoplasmic reticulum. The protein is not recognised and is degraded via ubiquitin tagging.  

CFTR is a member of the ABC superfamily of proteins and is the only Cl- channel in this family. It is very similar to P-glycoprotein, apart from the fact that CFTR contains a large regulatory domain (R domain). The CFTR gene was cloned in 1989.

CFTR is a passive transporter and it is special in the ABC superfamily proteins. It has got 12 transmembrane domains, with two nucleotide binding domains (NBD1 and NBD2) and a regulatory domain. The binding of ATP is essential for the function for the channel, NBD1 and NBD2 both bind ATP however only NBD2 can hydrolyse ATP.

CFTR is a disease caused by a mutation in the gene encoding CFTR protein, which functions as a CL- channel in the plasma membrane of epithelial cells. CFTR's main role is the regulation of ion concentration in the extracellular fluid. Many organs become affected by Cystic Fibrosis, which disrupts their normal functioning. A major problem is encountered in the lungs, where there is clogging of the bronchial passage and infection. Consequently those factors impede breathing and lungs are slowly destroyed. In liver, disease affects digestion, as it plugs in the small bile ducts. Organs which are altered by the disease are also pancreas, small intestine and the reproductive duct.

References

  1. Alberts, Bruce (2002), Molecular Biology Of The Cell, 4th edition, Garland Science
  2. Alberts, Bruce (2002), Molecular Biology Of The Cell, 4th edition, Garland Science
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