Question

Post-translational phosphorylation of proteins usually modify:

• A. Ser and Phe
• B. Thr and Val
• C. Ser, Thr, and Tyr
• D. Thr, Ala

Hint:

"STY" (Ser, Thr, Tyr) are the "Stay" points for phosphate groups.

Answer 1

The Correct Option is C

Step 1: Concept
Phosphorylation is a common post-translational modification where a phosphate group is added to an amino acid residue by a kinase.

Step 2: Meaning
For phosphorylation to occur, the amino acid side chain must possess a nucleophilic hydroxyl (—OH) group.

Step 3: Analysis
Serine (Ser), Threonine (Thr), and Tyrosine (Tyr) all contain hydroxyl groups in their side chains. Other amino acids like Phenylalanine (Phe), Valine (Val), and Alanine (Ala) lack the necessary functional group for standard enzymatic phosphorylation.

Step 4: Conclusion
Therefore, the trio of Ser, Thr, and Tyr are the primary targets for protein phosphorylation in eukaryotes. Final Answer: (C)