posttranslationally

Posttranslationally is an adverb used to describe events that occur to a protein after it has been synthesized by ribosomes during translation. In biology, many proteins undergo posttranslational processing or modifications that alter their function, stability, localization, or interactions. The term emphasizes that these changes happen after the polypeptide chain emerges from the ribosome.

Posttranslational modifications (PTMs) are diverse and can be enzymatic or non-enzymatic. Common examples include phosphorylation, glycosylation, acetylation, methylation, ubiquitination, and lipidation. Proteolytic processing, such as the removal of signal peptides or propeptides, is another form of posttranslational alteration that activates or matures proteins. Disulfide bond formation, hydroxylation, sulfation, and sumoylation are further instances. Many PTMs occur cotranslationally in the endoplasmic reticulum or Golgi apparatus, or after trafficking to specific cellular compartments, contributing to the dynamic regulation of protein behavior.

The functional consequences of posttranslationally modified proteins are broad. PTMs can regulate catalytic activity, alter binding partners, determine subcellular localization, modulate stability and degradation, or create docking sites for signaling complexes. Reversible modifications allow rapid and reversible control of cellular pathways, while irreversible changes can permanently redefine protein fate. Aberrations in posttranslational modifications are implicated in numerous diseases, making the study of these processes important for understanding biology and developing therapies.

Techniques such as mass spectrometry and targeted proteomics are used to identify and quantify PTMs. Interdisciplinary research examines how posttranslationally modified proteins integrate into cellular networks and respond to physiological changes.