Post-translational modifications (PTMs) are crucial processes that occur after the translation of proteins from messenger RNA (mRNA). Once a polypeptide chain is synthesized, various covalent alterations can take place, influencing the protein's functionality and activity. Understanding PTMs is essential for grasping how proteins are regulated within the cell.
Among the most common types of post-translational modifications are:
Methylation: This involves the addition of a methyl group (–CH3) to the protein, which can affect its interaction with other molecules.
Acetylation: In this modification, an acetyl group (–COCH3) is added, often influencing gene expression and protein stability.
Ubiquitination: This process adds a small protein called ubiquitin to the target protein, marking it for degradation or altering its cellular location.
Phosphorylation: The addition of a phosphate group (–PO4) can activate or deactivate enzymes and is a key regulatory mechanism in many signaling pathways.
Other notable PTMs include hydroxylation (addition of a hydroxyl group), lipidation (attachment of a lipid), disulfide bond formation (covalent linkages between cysteine residues), sulfonation (addition of a sulfur group), and glycosylation (attachment of carbohydrates). Each of these modifications plays a significant role in determining the protein's structure, function, and interactions within the cell.
As you study post-translational modifications, focus on the recommended types—methylation, acetylation, ubiquitination, and phosphorylation—as these are fundamental to understanding protein regulation and function in biological systems.