posttranslatsioalisesti

Posttranslational modification (PTM) refers to the covalent and generally enzymatic addition of chemical groups or proteins to a protein after its synthesis on the ribosome. This process occurs in all domains of life and plays a critical role in regulating protein function, localization, stability, and interactions. Unlike genetic mutations or alternative splicing, which alter the protein sequence at the DNA or RNA level, PTMs provide a dynamic mechanism to fine-tune cellular responses to environmental and developmental cues.

Common types of PTMs include phosphorylation, acetylation, methylation, ubiquitination, glycosylation, and sumoylation. Phosphorylation, for example, often modulates enzyme activity, signaling pathways, and cellular metabolism by adding a phosphate group to amino acids like serine, threonine, or tyrosine. Ubiquitination, on the other hand, tags proteins for degradation via the proteasome or alters their function, influencing processes such as DNA repair and immune responses. Glycosylation, primarily occurring in the endoplasmic reticulum and Golgi apparatus, affects protein folding, stability, and cell-cell recognition.

PTMs are tightly controlled by specific enzymes called writers (e.g., kinases for phosphorylation), erasers (e.g., phosphatases), and readers (e.g., protein domains that recognize modified sites). Dysregulation of PTMs has been linked to various diseases, including cancer, neurodegenerative disorders, and metabolic syndromes. For instance, aberrant phosphorylation of signaling proteins can lead to uncontrolled cell proliferation in cancer, while improper glycosylation is associated with conditions like diabetes and cystic fibrosis.

Research into PTMs has expanded rapidly with advances in mass spectrometry and bioinformatics, enabling large-scale mapping of modification sites across the proteome. Understanding PTMs is essential for developing targeted therapies and unraveling the complexities of cellular regulation. The field continues to evolve, highlighting the importance of posttranslational modifications in maintaining cellular homeostasis and responding to physiological demands.