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In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes , which translate mRNA into polypeptide chains , which may then change to form the mature protein product.
Post-translational modifications can occur before protein folding or after. Common biological methods of modifying peptide chains after translation include methylation, phosphorylation, and disulfide bond formation. Methylation often occurs to arginine or lysine and involves adding a methyl group to a nitrogen (replacing a hydrogen).
Transcriptional modification or co-transcriptional modification is a set of biological processes common to most eukaryotic cells by which an RNA primary transcript is chemically altered following transcription from a gene to produce a mature, functional RNA molecule that can then leave the nucleus and perform any of a variety of different functions in the cell. [1]
Glycosylation is a form of co-translational and post-translational modification. Glycans serve a variety of structural and functional roles in membrane and secreted proteins. [ 2 ] The majority of proteins synthesized in the rough endoplasmic reticulum undergo glycosylation.
Protein phosphorylation is the most abundant post-translational modification in eukaryotes. Phosphorylation can occur on serine , threonine and tyrosine side chains (in other words, on their residues) through phosphoester bond formation, on histidine , lysine and arginine through phosphoramidate bonds , and on aspartic acid and glutamic acid ...
Protein phosphorylation is a reversible post-translational modification of proteins. In eukaryotes, protein phosphorylation functions in cell signaling, gene expression, and differentiation. It is also involved in DNA replication during the cell cycle, and the mechanisms that cope with stress-induced replication blocks.
A common modification is prenylation of hydroxyl groups by an F protein prenyltransferase. Oxidation of azoline heterocycles to azoles can also be accomplished by an oxidase domain located on the G protein. Unusual for ribosomal peptides, cyanobactins can include D-amino acids; these can occur adjacent to azole or azoline residues. [1]
Histone rearrangement is facilitated by post-translational modifications to the tails of the core histones. A wide variety of modifications can be made by enzymes such as the histone acetyltransferases (HATs), histone methyltransferases (HMTs), and histone deacetylases (HDACs), among others. These enzymes can add or remove covalent ...