Amino Acids & Proteins MCAT Practice Question
A researcher studying protein misfolding discovers that a mutation in the CFTR protein replaces a phenylalanine residue with a serine in the nucleotide-binding domain. This mutation prevents proper protein folding and leads to proteasomal degradation. Phenylalanine is hydrophobic while serine is polar. Which of the following best explains why this substitution is particularly disruptive to protein structure?
Answer choices
- BPolar serine will repel the negatively charged phosphate groups in ATP
- DThe introduction of a polar residue disrupts hydrophobic core interactions essential for domain stabilityCorrect answer
- ASerine cannot form disulfide bonds with nearby cysteine residues
- CSerine is smaller and creates a cavity that destabilizes the tertiary structure
- EPhenylalanine residues are required for all protein-protein interactions in the cell
- FSerine lacks the aromatic ring structure necessary for π-π stacking interactions with tryptophan residues
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