6. Cystic fibrosis (CF) is an inherited disorder caused by different types of mu

Question

6. Cystic fibrosis (CF) is an inherited disorder caused by different types of mutations, many of which prevent ions from moving across cell membranes. Normally there are channel proteins that allow passage of the ions, but in patients with one kind of CF these proteins seem odd. Closer examination shows that these proteins display the correct amino acid sequence. However, they fail to do their job. A) Given that the primary structure of the protein is correct, what can you infer about the DNA sequence of this patient, is there a mutation? Explain. B) Why is the primary structure insufficient to guarantee the proper function of the protein?

Explanation / Answer

A) As the primary structure of the protein is correct so there is no mutation in the gene or DNA that codes for this protein.

B) But functioning of a protein does not depend upon only its primary structure, it is on a large part depends upon its secondary and tertiary structure which is produced due to protein folding. For example CFTR ( a CF protein) which acts as an ion channel through membrane has two transmembrane domain and two nucleotide-binding domain. Now these two domain are connected by regulatory R domain. This complete tertiary structure is required for the function of the protein to transport ions as a ABC transporter.

This higher order structures of proteins are produced with the help chaperone proteins, SNARE proteins atc.and on the functional level it is regulated by different protein kinases. Mutation in the DNA coding for any of these regulatory proteins can cause conformational distortion in the CF protein and thus stop the ion transport.

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