80. Phosphorylation of proteins is a typical post-translational modification which modulates their activities.
Which one of the following amino acid residues can be phosphorylated?
1. Glutamic acid
2. Lysine
3. Asparagine
4. Aspartic acid
Detailed Explanation
Phosphorylation is a common and crucial post-translational modification that regulates protein function by adding a phosphate group (PO4) to an amino acid residue. This modification typically occurs on certain amino acid residues that have a hydroxyl group (-OH) in their side chains, which makes them receptive to the addition of phosphate groups. The main residues involved in phosphorylation are:
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Serine (Ser)
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Threonine (Thr)
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Tyrosine (Tyr)
These amino acids have hydroxyl groups that serve as acceptors for phosphate groups. Among the options given—glutamic acid, lysine, asparagine, and aspartic acid—none of these are typically phosphorylated.
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Glutamic acid and aspartic acid have carboxyl groups, not hydroxyl groups, and are generally not involved in phosphorylation.
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Lysine has an amino group and is involved in other post-translational modifications such as acetylation, but not phosphorylation.
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Asparagine contains an amide group, which is also not conducive to phosphorylation.
In contrast, the amino acids serine, threonine, and tyrosine contain hydroxyl groups and are commonly phosphorylated in various cellular processes such as signal transduction, cell cycle regulation, and enzyme activity control.
Therefore, the correct answer is none of the listed options (Glutamic acid, Lysine, Asparagine, and Aspartic acid) are typically phosphorylated, and the correct phosphorylatable amino acids are serine, threonine, and tyrosine.
This content explains phosphorylation as a post-translational modification and clarifies which amino acids are typically involved in this process.
