Post-Translational Modification (PTM)
Definition:
Post-translational modification refers to the chemical changes that occur to a newly synthesized
polypeptide chain after translation. These modifications happen in the endoplasmic reticulum
(ER) and Golgi apparatus in eukaryotic cells and are essential for converting an inactive
polypeptide into a functional, mature protein.
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Types of Post-Translational Modifications:
1. Phosphorylation:
Addition of phosphate group (usually to serine, threonine, or tyrosine residues).
Enzyme: Kinase
Example: Regulation of enzymes like glycogen phosphorylase.
2. Glycosylation:
Attachment of carbohydrate chains to proteins.
Helps in protein folding, stability, and cell signaling.
Example: Glycoproteins in cell membranes.
3. Hydroxylation:
Addition of hydroxyl group (-OH) to amino acids like proline or lysine.
Important for collagen stability.
4. Methylation:
Addition of methyl group to lysine or arginine residues.
Influences gene expression and chromatin structure.
5. Acetylation:
Addition of an acetyl group to the N-terminal or lysine residues.
Regulates protein stability and gene transcription (e.g., histone acetylation).
Definition:
Post-translational modification refers to the chemical changes that occur to a newly synthesized
polypeptide chain after translation. These modifications happen in the endoplasmic reticulum
(ER) and Golgi apparatus in eukaryotic cells and are essential for converting an inactive
polypeptide into a functional, mature protein.
---
Types of Post-Translational Modifications:
1. Phosphorylation:
Addition of phosphate group (usually to serine, threonine, or tyrosine residues).
Enzyme: Kinase
Example: Regulation of enzymes like glycogen phosphorylase.
2. Glycosylation:
Attachment of carbohydrate chains to proteins.
Helps in protein folding, stability, and cell signaling.
Example: Glycoproteins in cell membranes.
3. Hydroxylation:
Addition of hydroxyl group (-OH) to amino acids like proline or lysine.
Important for collagen stability.
4. Methylation:
Addition of methyl group to lysine or arginine residues.
Influences gene expression and chromatin structure.
5. Acetylation:
Addition of an acetyl group to the N-terminal or lysine residues.
Regulates protein stability and gene transcription (e.g., histone acetylation).
