Posttranslaatio

Posttranslation is a crucial stage in gene expression that occurs after protein synthesis. During translation, ribosomes assemble amino acids into polypeptide chains based on the mRNA sequence. However, the newly synthesized polypeptide, or primary transcript, is often not yet functional. Posttranslational modifications are chemical alterations that occur to proteins after their synthesis. These modifications can significantly alter a protein's structure, function, stability, and localization within the cell.

There are a wide variety of posttranslational modifications, with over 200 known types. Some of the most common include phosphorylation, which involves the addition of a phosphate group, and glycosylation, the attachment of carbohydrate molecules. Other significant modifications include ubiquitination, methylation, acetylation, and proteolytic cleavage. These modifications can act as molecular switches, turning protein activity on or off, or they can be essential for proper protein folding and assembly into larger complexes.

The types and extent of posttranslational modifications are highly specific to each protein and the cellular context. They play vital roles in virtually all cellular processes, including signal transduction, metabolism, immune response, and DNA repair. Aberrant posttranslational modifications are often linked to various diseases, highlighting their importance in maintaining cellular homeostasis. Understanding these modifications is therefore central to comprehending cellular function and developing therapeutic strategies.