Posttranslational modification

Post-translational modification (PTM) is the protein biosynthesis for many proteins. A protein (also called a disulfide bridges.

Also, insulin is cut twice after disulfide bonds are formed, and a propeptide is removed from the middle of the chain; the resulting protein consists of two polypeptide chains connected by disulfide bonds.

Other modifications, like phosphorylation, are part of common mechanisms for controlling the behavior of a protein, for instance activating or inactivating an enzyme.

PTMs involving addition of functional groups

PTMs involving addition include:

acylation
- acetylation, the addition of an acetyl group, usually at the N-terminus of the protein
alkyl group (e.g. methyl, ethyl)
- arginine residues. (This is a type of alkylation.)
- demethylation
amidation at C-terminus
biotinylation, acylation of conserved lysine residues with a biotin appendage
formylation
gamma-carboxylation dependent on Vitamin K^[2]
glutamylation, covalent linkage of glutamic acid residues to tubulin and some other proteins.^[3] (See tubulin polyglutamylase)
glycation, which is regarded as a nonenzymatic attachment of sugars.
glycylation, covalent linkage of one to more than 40 glycine residues to the tubulin C-terminal tail
heme moiety may be covalently attached
hydroxylation
iodination (e.g. of thyroid hormones)
isoprenylation, the addition of an isoprenoid group (e.g. farnesol and geranylgeraniol)
lipoylation, attachment of a lipoate functionality
- prenylation
- GPI anchor formation
  - myristoylation
  - farnesylation
  - geranylgeranylation
nucleotides or derivatives thereof may be covalently attached
- ADP-ribosylation
- flavin attachment
oxidation
pegylation
phosphatidylinositol may be covalently attached
phosphopantetheinylation, the addition of a 4'-phosphopantetheinyl moiety from coenzyme A, as in fatty acid, polyketide, non-ribosomal peptide and leucine biosynthesis
histidine
pyroglutamate formation
racemization of prolyl isomerase
tRNA-mediation addition of amino acids such as arginylation
tyrosine.
Selenoylation (co-translational incorporation of selenoproteins)
Sulfation

PTMs involving addition of other proteins or peptides

ISGylation, the covalent linkage to the ISG15 protein (Interferon-Stimulated Gene 15)^[4]
SUMO protein (Small Ubiquitin-related MOdifier)^[5]
covalent linkage to the protein ubiquitin.

PTMs involving changing the chemical nature of amino acids

PTMs involving structural changes

cysteine amino acids
proteolytic cleavage, cleavage of a protein at a peptide bond

Case examples

cleavage and formation of disulfide bridges during the production of insulin
PTM of RNA polymerase control by chromatin structure
PTM of RNA polymerase II as regulation of transcription: RNA polymerase II

References

^ Gramatikoff K. in Abgent Catalog (2004-5) p.263
^ Walker, 2001 [1]
^ [2]
^ Malakhova, Oxana A.; Yan, Ming; Malakhov, Michael P.; Yuan, Youzhong; Ritchie, Kenneth J.; Kim, Keun Il; Peterson, Luke F.; Shuai, Ke; and Dong-Er Zhang. (2003). Protein ISGylation modulates the JAK-STAT signaling pathway. Genes & Development 17 (4), 455-460.
^ Van G. Wilson (Ed.) (2004). Sumoylation: Molecular Biology and Biochemistry. Horizon Bioscience. ISBN 0-9545232-8-8.

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Categories: Posttranslational modification

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