🧬AP Biology
3. Cystic fibrosis is a genetic disorder caused by mutations in the gene encoding the CFTR protein, which functions as a chloride channel in cell membranes. The correct function of CFTR depends on its specific three-dimensional structure. The most common mutation, F508, results in the deletion of a single phenylalanine amino acid residue. This deletion causes the protein to misfold, leading to its degradation by the cell before it can reach the plasma membrane.
Scientists hypothesized that a small molecule drug, Compound X, could stabilize the mutant CFTR protein and improve its transport to the plasma membrane. To test this, they cultured epithelial cells expressing the F508 CFTR mutation. The cells were divided into four treatment groups and incubated for 24 hours in growth media containing 0 M, 1 M, 10 M, or 100 M of Compound X. Following incubation, the scientists isolated the plasma membranes from the cells and measured the relative amount of CFTR protein present in each group.
Describe how the interactions between amino acid R-groups (side chains) contribute to the formation of the tertiary structure of a protein.
Identify the negative control group used in the experiment.
Predict how the relative amount of CFTR protein in the plasma membrane will change across the four treatment groups (0 μM, 1 μM, 10 μM, and 100 μM of Compound X). Provide a specific prediction for the pattern of results you expect to observe.
Phenylalanine is an amino acid with a nonpolar R-group. The scientists claim that the deletion of phenylalanine at position 508 destabilizes the hydrophobic core of the CFTR protein. Justify your prediction in Part C by explaining how the chemical properties of water and amino acids support the relationship between the ΔF508 mutation and the effects of Compound X on CFTR protein stability and localization.
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