Discuss the role of claudins in the structure and functions of tight junctions. Propose what might change for a tight junction in which charged amino acids in the claudin large extracellular loop are mutated to nonpolar amino acids

Question

What will be an ideal response?

Answer 1

Answer: Claudin extracellular loop domains form homophilic interactions that are a barrier to paracellular transport through intercellular spaces between epithelial cells. Charged amino acids in the claudin large extracellular loop form ion-selective pores that allow the passage of specific ions through the barrier. Mutation of the charged amino acids to nonpolar ones would create a more hydrophobic region that could block ion transport but allow passage of nonpolar substances that fail to pass through wild-type claudins. This would change the barrier function of the tissue and could affect the health of the organism. Recessive mutations in one type of claudin result in an inherited disorder characterized by severe Mg2+ and Ca2+ imbalance.