Question

What’s post-translational modification? Give same examples. If you find a selenoCys in a protein, what mechanism is responsible for the incorporation of selenoCys?

Answer 1

• It refers to the chemical chnages that the protein might undergo after Translation ( Enzymatic modifications of protein following Protein Biosynthesis)
• It plays a fundamental role in regulating protein folding, their targetting to subcelullar components etc.
• There are different types of post translation modifications:

1. Phosphorylation
2. Glycosylation
3. Ubiquitination
4. Nitrosylation
5. Methylation
6. Acetylation
7. Lipidation
8. Proteolysis

EXAMPLES:

• Kinases phosphorylate proteins at specific amino acids side chains, a common method for catalytic activation/inactivation.
• Zymogens are inactive forms of enzymes. They are activated by the removal of some portion of the protein.

Expressed Protein Ligation is a frequently used technique to insert non-standrard amino acids into proteins. Therefore, selenoCys is incorporated into the proteins using Peptide Ligation.