Post-translational modification
Molecular Biology · Biochemistry · Proteomics
Say it: pohst-tranz-LAY-shun-ul mod-ih-fih-KAY-shun
A post-translational modification is a chemical change made to a protein after it is built on the ribosome, often altering its activity or location.
Also: PTM, posttranslational modification, post-translational modifications
Definition
What is a post-translational modification?
When a ribosome finishes translating a messenger RNA, the new chain of amino acids is often not yet a working protein. Post-translational modifications (PTMs) are the enzyme-driven changes made afterward. They include adding small chemical groups such as phosphate (phosphorylation), acetyl or methyl groups; attaching sugar chains (glycosylation); linking a small protein called ubiquitin; and cutting the chain at set points, as when insulin is trimmed from a longer precursor.
These changes greatly expand what a limited set of genes can do. Phosphorylation by enzymes called kinases acts like an on-off switch and is central to cell signaling. Glycosylation, which takes place in the endoplasmic reticulum and Golgi apparatus, helps many proteins fold and reach the cell surface. A chain of ubiquitin marks a protein for destruction by the proteasome. Other marks decide whether a protein stays in the cytoplasm, enters the nucleus or binds the membrane, and many can be reversed, letting cells respond quickly.
Because PTMs change a protein's mass, mass spectrometry is the main way to detect them in proteomics.
Word parts
Where does the term “post-translational modification” come from?
- post-
- afterLatin post
- translation
- protein synthesis; literally carried acrossLatin translatus
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Related
Terms that go with it
- TranslationTranslation is the process in which a ribosome reads the codons of a messenger RNA and links amino acids in that order to build a protein.
- ProteinA protein is a large molecule made of one or more chains of amino acids, folded into a specific shape that determines its job in the body.
- ProteomicsProteomics is the large-scale study of the proteome, the full set of proteins in a cell, tissue or organism, including their amounts, changes and interactions.
- Mass spectrometryMass spectrometry is an analytical technique that turns molecules into charged ions and sorts them by mass-to-charge ratio to identify and measure them.
- EnzymeAn enzyme is a biological catalyst, usually a protein, that speeds up a specific chemical reaction without being used up in the process.
- Golgi apparatusThe Golgi apparatus is a stack of flattened membrane sacs that modifies, sorts and packages proteins and lipids sent from the endoplasmic reticulum.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 16.6 Eukaryotic Translational and Post-translational Gene Regulation
- NCBI MeSH: Protein Processing, Post-Translational
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