A missense mutation changes the codon GCC (alanine) to GAC (aspartic acid). If this mutation occurs in the active site of an enzyme, predict its impact on the enzyme’s tertiary structure and catalytic activity.
Answer
Introduction of a negative charge disrupts hydrophobic interactions, altering the enzyme’s 3‑D structure and reducing catalytic activity.
Step-by-step solution
- Identify the amino acids: GCC codes for alanine (non‑polar) and GAC codes for aspartic acid (acidic).
- Note the change from a non‑polar to an acidic residue introduces a negative charge.
- In an active site, hydrophobic interactions are crucial for maintaining the proper fold.
- Replacing alanine with aspartic acid disrupts these interactions.
- The resulting change in charge and side‑chain size can distort the local 3‑D structure.
- Such distortion typically reduces or abolishes catalytic activity.
- Therefore, the enzyme’s tertiary structure and function are compromised.
Common mistake: Overlooking the charge change and its structural consequences
Concept tested: Missense mutation effect on enzyme structure
Published · How this solution was prepared and checked
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