186. Proteins usually have hydrophobic interiors or cores and hydrophilic exteriors. If a protein
comprises hydrophobic patches on its outer surface, what can it mean?
A. The protein is unstable
B. Structure prediction was done wrongly
C. It could be part of a multimeric protein complex
D. It is a DNA-binding protein

Explanation:

Typically, proteins fold such that:

• Hydrophobic residues are buried in the core to avoid contact with water.

• Hydrophilic residues are exposed on the surface, interacting with the aqueous environment.

However, if hydrophobic patches are found on the surface of a properly folded protein, this can suggest a functional purpose, rather than a structural anomaly.

Key Insight:

Hydrophobic surface patches are often involved in:

• Protein-protein interactions

• Oligomerization or multimerization

• Membrane association (in some cases)

Thus, proteins that are part of multimeric complexes may expose hydrophobic regions on their surfaces to interact with the corresponding hydrophobic regions of other subunits.

Why Other Options Are Incorrect:

• A. The protein is unstable – Not necessarily; exposed hydrophobic patches could be functional.

• B. Structure prediction was done wrongly – Hydrophobic surface areas may occur even in correctly predicted or solved structures, especially in complexes.

• D. It is a DNA-binding protein – DNA-binding proteins usually have positively charged or polar regions for interaction with the negatively charged DNA backbone.

Conclusion:

The presence of hydrophobic patches on a protein’s surface commonly indicates that the protein may participate in multimeric or protein-protein interactions, forming complexes or quaternary structures.

Correct Answer: C