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Post-translational modification of insulin. At the top, the ribosome translates a mRNA sequence into a protein, insulin, and passes the protein through the endoplasmic reticulum, where it is cut, folded and held in shape by disulfide (-S-S-) bonds. Then the protein passes through the golgi apparatus, where it is packaged into a vesicle. In the vesicle, more parts are cut off, and it turns into mature insulin.

Post-translational modification (PTM) refers to the covalent and generally enzymatic modification of proteins during or after protein biosynthesis. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling.

Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini.^[1] They can extend the chemical repertoire of the 20 standard amino acids by introducing new functional groups such as phosphate, acetate, amide groups, or methyl groups. Phosphorylation is a very common mechanism for regulating the activity of enzymes and is the most common post-translational modification.^[2] Many eukaryotic proteins also have carbohydrate molecules attached to them in a process called glycosylation, which can promote protein folding and improve stability as well as serving regulatory functions. Attachment of lipid molecules, known as lipidation, often targets a protein or part of a protein to the cell membrane.

Other forms of post-translational modification consist of cleaving peptide bonds, as in processing a propeptide to a mature form or removing the initiator methionine residue. The formation of disulfide bonds from cysteine residues may also be referred to as a post-translational modification.^[3]^:17.6 For instance, the peptide hormone 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.

Some types of post-translational modification are consequences of oxidative stress. Carbonylation is one example that targets the modified protein for degradation and can result in the formation of protein aggregates.^[4]^[5] Specific amino acid modifications can be used as biomarkers indicating oxidative damage.^[6]

Sites that often undergo post-translational modification are those that have a functional group that can serve as a nucleophile in the reaction: the hydroxyl groups of serine, threonine, and tyrosine; the amine forms of lysine, arginine, and histidine; the thiolate anion of cysteine; the carboxylates of aspartate and glutamate; and the N- and C-termini. In addition, although the amides of asparagine and glutamine are weak nucleophiles, both can serve as attachment points for glycans. Rarer modifications can occur at oxidized methionines and at some methylenes in side chains.^[7]^:12–14

Post-translational modification of proteins can be experimentally detected by a variety of techniques, including mass spectrometry, Eastern blotting, and Western blotting.

1 PTMs involving addition of functional groups
- 1.1 Addition by an enzyme in vivo
  - 1.1.1 Hydrophobic groups for membrane localization
  - 1.1.2 Cofactors for enhanced enzymatic activity
  - 1.1.3 Modifications of translation factors
  - 1.1.4 Smaller chemical groups
- 1.2 Non-enzymatic additions in vivo
- 1.3 Non-enzymatic additions in vitro
2 Other proteins or peptides
3 Chemical modification of amino acids
4 Structural changes
5 Post-translational modification statistics
6 Case examples
7 See also
8 External links
9 References

PTMs involving addition of functional groups

The genetic code diagram^[8] showing the amino acid residues as target of modification.

Addition by an enzyme in vivo

Hydrophobic groups for membrane localization

myristoylation, attachment of myristate, a C₁₄ saturated acid
palmitoylation, attachment of palmitate, a C₁₆ saturated acid
isoprenylation or prenylation, the addition of an isoprenoid group (e.g. farnesol and geranylgeraniol)
- farnesylation
- geranylgeranylation
glypiation, glycosylphosphatidylinositol (GPI) anchor formation via an amide bond to C-terminal tail

Cofactors for enhanced enzymatic activity

lipoylation, attachment of a lipoate (C₈) functional group
flavin moiety (FMN or FAD) may be covalently attached
heme C attachment via thioether bonds with cysteins
phosphopantetheinylation, the addition of a 4'-phosphopantetheinyl moiety from coenzyme A, as in fatty acid, polyketide, non-ribosomal peptide and leucine biosynthesis
retinylidene Schiff base formation

Modifications of translation factors

diphthamide formation (on a histidine found in eEF2)
ethanolamine phosphoglycerol attachment (on glutamate found in eEF1α)^[9]
hypusine formation (on conserved lysine of eIF5A (eukaryotic) and aIF5A (archaeal))

Smaller chemical groups

acylation, e.g. O-acylation (esters), N-acylation (amides), S-acylation (thioesters)
- acetylation, the addition of an acetyl group, either at the N-terminus ^[10] of the protein or at lysine residues.^[11] See also histone acetylation.^[12]^[13] The reverse is called deacetylation.
- formylation
alkylation, the addition of an alkyl group, e.g. methyl, ethyl
- methylation the addition of a methyl group, usually at lysine or arginine residues. The reverse is called demethylation.
amide bond formation
- amidation at C-terminus
- amino acid addition
  - arginylation, a tRNA-mediation addition
  - polyglutamylation, covalent linkage of glutamic acid residues to the N-terminus of tubulin and some other proteins.^[14] (See tubulin polyglutamylase)
  - polyglycylation, covalent linkage of one to more than 40 glycine residues to the tubulin C-terminal tail
butyrylation
gamma-carboxylation dependent on Vitamin K^[15]
glycosylation, the addition of a glycosyl group to either arginine, asparagine, cysteine, hydroxylysine, serine, threonine, tyrosine, or tryptophan resulting in a glycoprotein. Distinct from glycation, which is regarded as a nonenzymatic attachment of sugars.
- polysialylation, addition of polysialic acid, PSA, to NCAM
malonylation
hydroxylation
iodination (e.g. of thyroglobulin)
nucleotide addition such as ADP-ribosylation
oxidation
phosphate ester (O-linked) or phosphoramidate (N-linked) formation
- phosphorylation, the addition of a phosphate group, usually to serine, threonine, and tyrosine (O-linked), or histidine (N-linked)
- adenylylation, the addition of an adenylyl moiety, usually to tyrosine (O-linked), or histidine and lysine (N-linked)
propionylation
pyroglutamate formation
S-glutathionylation
S-nitrosylation
succinylation addition of a succinyl group to lysine
sulfation, the addition of a sulfate group to a tyrosine.

Non-enzymatic additions in vivo

glycation, the addition of a sugar molecule to a protein without the controlling action of an enzyme.

Non-enzymatic additions in vitro

biotinylation, acylation of conserved lysine residues with a biotin appendage
pegylation

Other proteins or peptides

ISGylation, the covalent linkage to the ISG15 protein (Interferon-Stimulated Gene 15)^[16]
SUMOylation, the covalent linkage to the SUMO protein (Small Ubiquitin-related MOdifier)^[17]
ubiquitination, the covalent linkage to the protein ubiquitin.
Neddylation, the covalent linkage to Nedd
Pupylation, the covalent linkage to the Prokaryotic ubiquitin-like protein

Chemical modification of amino acids

citrullination, or deimination, the conversion of arginine to citrulline
deamidation, the conversion of glutamine to glutamic acid or asparagine to aspartic acid
eliminylation, the conversion to an alkene by beta-elimination of phosphothreonine and phosphoserine, or dehydration of threonine and serine, as well as by decarboxylation of cysteine ^[18]
carbamylation, the conversion of lysine to homocitrulline ^[19]

Structural changes

disulfide bridges, the covalent linkage of two cysteine amino acids
proteolytic cleavage, cleavage of a protein at a peptide bond
racemization
- of proline by prolyl isomerase
- of serine by protein-serine epimerase
- of alanine in dermorphin, a frog opioid peptide
- of methionine in deltorphin, also a frog opioid peptide
protein splicing, self-catalytic removal of inteins analogous to mRNA processing

Post-translational modification statistics

Recently, statistics of each post-translational modification experimentally and putatively detected have been compiled using proteome-wide information from the Swiss-Prot database.^[20] These statistics can be found at http://selene.princeton.edu/PTMCuration/.

Case examples

Cleavage and formation of disulfide bridges during the production of insulin
PTM of histones as regulation of transcription: RNA polymerase control by chromatin structure
PTM of RNA polymerase II as regulation of transcription
Cleavage of polypeptide chains as crucial for lectin specificity

External links

dbPTM - database of protein post-translational modifications
List of posttranslational modifications in ExPASy
Browse SCOP domains by PTM — from the dcGO database
Statistics of each post-translational modification from the Swiss-Prot database
AutoMotif Server - A Computational Protocol for Identification of Post-Translational Modifications in Protein Sequences
Functional analyses for site-specific phosphorylation of a target protein in cells
Detection of Post-Translational Modifications after high-accuracy MSMS

References

^ Pratt, Donald Voet; Judith G. Voet; Charlotte W. (2006). Fundamentals of biochemistry : life at the molecular level (2. ed.). Hoboken, NJ: Wiley. ISBN 0-471-21495-7.
^ Khoury, GA; Baliban, RC; Floudas, CA (13 September 2011). "Proteome-wide post-translational modification statistics: frequency analysis and curation of the swiss-prot database.". Scientific reports 1. PMID 22034591.
^ al.], Harvey Lodish ... [et (2000). Molecular cell biology (4th ed.). New York: Scientific American Books. ISBN 0-7167-3136-3.
^ Dalle-Donne, Isabella; Aldini, Giancarlo; Carini, Marina; Colombo, Roberto; Rossi, Ranieri; Milzani, Aldo (2006). "Protein carbonylation, cellular dysfunction, and disease progression". Journal of Cellular and Molecular Medicine 10 (2): 389–406. doi:10.1111/j.1582-4934.2006.tb00407.x. PMID 16796807.
^ Grimsrud, P. A.; Xie, H.; Griffin, T. J.; Bernlohr, D. A. (2008). "Oxidative Stress and Covalent Modification of Protein with Bioactive Aldehydes". Journal of Biological Chemistry 283 (32): 21837–41. doi:10.1074/jbc.R700019200. PMC 2494933. PMID 18445586.
^ Gianazza, E; Crawford, J; Miller, I (July 2007). "Detecting oxidative post-translational modifications in proteins.". Amino acids 33 (1): 51–6. PMID 17021655.
^ Walsh,, Christopher T. (2006). Posttranslational modification of proteins : expanding nature's inventory. Englewood: Roberts and Co. Publ. ISBN 9780974707730.
^ Gramatikoff K. in Abgent Catalog (2004-5) p.263
^ Whiteheart SW, Shenbagamurthi P, Chen L; et al. (1989). "Murine elongation factor 1 alpha (EF-1 alpha) is posttranslationally modified by novel amide-linked ethanolamine-phosphoglycerol moieties. Addition of ethanolamine-phosphoglycerol to specific glutamic acid residues on EF-1 alpha". J. Biol. Chem. 264 (24): 14334–41. PMID 2569467.
^ Polevoda B, Sherman F; Sherman (2003). "N-terminal acetyltransferases and sequence requirements for N-terminal acetylation of eukaryotic proteins". J Mol Biol 325 (4): 595–622. doi:10.1016/S0022-2836(02)01269-X. PMID 12507466.
^ Yang XJ, Seto E; Seto (2008). "Lysine acetylation: codified crosstalk with other posttranslational modifications". Mol Cell 31 (4): 449–61. doi:10.1016/j.molcel.2008.07.002. PMC 2551738. PMID 18722172.
^ Bártová E, Krejcí J, Harnicarová A, Galiová G, Kozubek S; Krejcí; Harnicarová; Galiová; Kozubek (2008). "Histone modifications and nuclear architecture: a review". J Histochem Cytochem 56 (8): 711–21. doi:10.1369/jhc.2008.951251. PMC 2443610. PMID 18474937.
^ Glozak MA, Sengupta N, Zhang X, Seto E; Sengupta; Zhang; Seto (2005). "Acetylation and deacetylation of non-histone proteins". Gene 363: 15–23. doi:10.1016/j.gene.2005.09.010. PMID 16289629.
^ Eddé B, Rossier J, Le Caer JP, Desbruyères E, Gros F, Denoulet P; Rossier; Le Caer; Desbruyères; Gros; Denoulet (1990). "Posttranslational glutamylation of alpha-tubulin". Science 247 (4938): 83–5. Bibcode:1990Sci...247...83E. doi:10.1126/science.1967194. PMID 1967194.
^ Walker CS, Shetty RP, Clark K; et al. (2001). "On a potential global role for vitamin K-dependent gamma-carboxylation in animal systems. Animals can experience subvaginal hemototitis as a result of this linkage. Evidence for a gamma-glutamyl carboxylase in Drosophila". J. Biol. Chem. 276 (11): 7769–74. doi:10.1074/jbc.M009576200. PMID 11110799.
^ 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): 455–60. doi:10.1101/gad.1056303. PMC 195994. PMID 12600939.
^ Van G. Wilson (Ed.) (2004). Sumoylation: Molecular Biology and Biochemistry. Horizon Bioscience. ISBN 0-9545232-8-8.
^ Brennan DF, Barford D; Barford (2009). "Eliminylation: a post-translational modification catalyzed by phosphothreonine lyases". Trends in Biochemical Sciences 34 (3): 108–114. doi:10.1016/j.tibs.2008.11.005. PMID 19233656.
^ Piotr Mydel, Zeneng Wang, Mikael Brisslert, Annelie Hellvard, Leif E. Dahlberg, Stanley L. Hazen and Maria Bokarewa (2010). "Carbamylation-dependent activation of T cells: a novel mechanism in the pathogenesis of autoimmune arthritis". Journal of Immunology 184 (12): 6882–6890. doi:10.4049/jimmunol.1000075. PMC 2925534. PMID 20488785.
^ Khoury, George A.; Baliban, Richard C.; and Christodoulos A. Floudas (2011). "Proteome-wide post-translational modification statistics: frequency analysis and curation of the swiss-prot database". Scientific Reports 1 (90): 90. Bibcode:2011NatSR...1E..90K. doi:10.1038/srep00090.

UpToDate Contents

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1. 胃腸ペプチドの合成、分泌、および調節 synthesis secretion and regulation of gastrointestinal peptides
2. 免疫系に対するステロイドの影響 glucocorticoid effects on the immune system
3. リウマチ性疾患におけるサイトカインネットワーク：治療の意味 cytokine networks in rheumatic diseases implications for therapy
4. コレシストキニンの生理学 physiology of cholecystokinin
5. C型肝炎ウイルスの特性 characteristics of the hepatitis c virus

English Journal

Regulation of sodium glucose co-transporter SGLT1 through altered glycosylation in the intestinal epithelial cells.

Arthur S1, Coon S2, Kekuda R3, Sundaram U4.Author information 1Department of Clinical and Translational Sciences, Joan C Edwards School of Medicine, Marshall University, 1400 Hal Greer Blvd., Huntington, WV 25701, USA.2Boston University Medical Center, Boston, MA 02118, USA.3Department of Pediatrics, West Virginia University, Morgantown, WV 26506, USA.4Department of Clinical and Translational Sciences, Joan C Edwards School of Medicine, Marshall University, 1400 Hal Greer Blvd., Huntington, WV 25701, USA. Electronic address: sundaramu@marshall.edu.AbstractInhibition of constitutive nitric oxide (cNO) production inhibits SGLT1 activity by a reduction in the affinity for glucose without a change in Vmax in intestinal epithelial cells (IEC-18). Thus, we studied the intracellular pathway responsible for the posttranslational modification/s of SGLT1. NO is known to mediate its effects via cGMP which is diminished tenfold in L-NAME treated cells. Inhibition of cGMP production at the level of guanylyl cyclase or inhibition of protein kinase G also showed reduced SGLT1 activity demonstrating the involvement of PKG pathway in the regulation of SGLT1 activity. Metabolic labeling and immunoprecipitation with anti-SGLT1 specific antibodies did not show any significant changes in phosphorylation of SGLT1 protein. Tunicamycin to inhibit glycosylation reduced SGLT1 activity comparable to that seen with L-NAME treatment. The mechanism of inhibition was secondary to decreased affinity without a change in Vmax. Immunoblots of luminal membranes from tunicamycin treated or L-NAME treated IEC-18 cells showed a decrease in the apparent molecular size of SGLT1 protein to 62 and 67kD, respectively suggesting an alteration in protein glycosylation. The deglycosylation assay with PNGase-F treatment reduced the apparent molecular size of the specific immunoreactive band of SGLT1 from control and L-NAME treated IEC-18 cells to approximately 62kD from their original molecular size of 75kD and 67kD, respectively. Thus, the posttranslational mechanism responsible for the altered affinity of SGLT1 when cNO is diminished is secondary to altered glycosylation of SGLT1 protein. The intracellular pathway responsible for this alteration is cGMP and its dependent kinase.
Biochimica et biophysica acta.Biochim Biophys Acta.2014 May;1838(5):1208-14. doi: 10.1016/j.bbamem.2014.01.002. Epub 2014 Jan 9.
Inhibition of constitutive nitric oxide (cNO) production inhibits SGLT1 activity by a reduction in the affinity for glucose without a change in Vmax in intestinal epithelial cells (IEC-18). Thus, we studied the intracellular pathway responsible for the posttranslational modification/s of SGLT1. NO i
PMID 24412219

Cell-free synthesis of membrane proteins: Tailored cell models out of microsomes.

Fenz SF1, Sachse R2, Schmidt T1, Kubick S3.Author information 1Leiden Institute of Physics, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands.2Fraunhofer IBMT, Branch Potsdam-Golm, Group of Cell-free Protein Synthesis, Am Mühlenberg 13, 14476 Potsdam, Germany.3Fraunhofer IBMT, Branch Potsdam-Golm, Group of Cell-free Protein Synthesis, Am Mühlenberg 13, 14476 Potsdam, Germany. Electronic address: Stefan.Kubick@ibmt.fraunhofer.de.AbstractIncorporation of proteins in biomimetic giant unilamellar vesicles (GUVs) is one of the hallmarks towards cell models in which we strive to obtain a better mechanistic understanding of the manifold cellular processes. The reconstruction of transmembrane proteins, like receptors or channels, into GUVs is a special challenge. This procedure is essential to make these proteins accessible to further functional investigation. Here we describe a strategy combining two approaches: cell-free eukaryotic protein expression for protein integration and GUV formation to prepare biomimetic cell models. The cell-free protein expression system in this study is based on insect lysates, which provide endoplasmic reticulum derived vesicles named microsomes. It enables signal-induced translocation and posttranslational modification of de novo synthesized membrane proteins. Combining these microsomes with synthetic lipids within the electroswelling process allowed for the rapid generation of giant proteo-liposomes of up to 50μm in diameter. We incorporated various fluorescent protein-labeled membrane proteins into GUVs (the prenylated membrane anchor CAAX, the heparin-binding epithelial growth factor like factor Hb-EGF, the endothelin receptor ETB, the chemokine receptor CXCR4) and thus presented insect microsomes as functional modules for proteo-GUV formation. Single-molecule fluorescence microscopy was applied to detect and further characterize the proteins in the GUV membrane. To extend the options in the tailoring cell models toolbox, we synthesized two different membrane proteins sequentially in the same microsome. Additionally, we introduced biotinylated lipids to specifically immobilize proteo-GUVs on streptavidin-coated surfaces. We envision this achievement as an important first step toward systematic protein studies on technical surfaces.
Biochimica et biophysica acta.Biochim Biophys Acta.2014 May;1838(5):1382-8. doi: 10.1016/j.bbamem.2013.12.009. Epub 2013 Dec 25.
Incorporation of proteins in biomimetic giant unilamellar vesicles (GUVs) is one of the hallmarks towards cell models in which we strive to obtain a better mechanistic understanding of the manifold cellular processes. The reconstruction of transmembrane proteins, like receptors or channels, into GUV
PMID 24370776

Association of prion protein genotype and scrapie prion protein type with cellular prion protein charge isoform profiles in cerebrospinal fluid of humans with sporadic or familial prion diseases.

Schmitz M1, Lüllmann K2, Zafar S2, Ebert E2, Wohlhage M2, Oikonomou P2, Schlomm M2, Mitrova E3, Beekes M4, Zerr I2.Author information 1Department of Neurology, Clinical Dementia Center and DZNE Georg-August University, Göttingen, Germany. Electronic address: matthias.schmitz@med.uni-goettingen.de.2Department of Neurology, Clinical Dementia Center and DZNE Georg-August University, Göttingen, Germany.3Slovak Medical University, Bratislava, Slovakia.4Robert Koch-Institute, FG 14 - AG 5: Work Group Unconventional Pathogens and Their Inactivation, Division of Applied Infection Control and Nosocomial Hygiene, Berlin, Germany.AbstractThe present study investigates whether posttranslational modifications of cellular prion protein (PrP(C)) in the cerebrospinal fluid (CSF) of humans with prion diseases are associated with methionine (M) and/or valine (V) polymorphism at codon 129 of the prion protein gene (PRNP), scrapie prion protein (PrP(Sc)) type in sporadic Creutzfeldt-Jakob disease (sCJD), or PRNP mutations in familial Creutzfeldt-Jakob disease (fCJD/E200K), and fatal familial insomnia (FFI). We performed comparative 2-dimensional immunoblotting of PrP(C) charge isoforms in CSF samples from cohorts of diseased and control donors. Mean levels of total PrP(C) were significantly lower in the CSF from fCJD patients than from those with sCJD or FFI. Of the 12 most abundant PrP(C) isoforms in the examined CSF, one (IF12) was relatively decreased in (1) sCJD with VV (vs. MM or MV) at PRNP codon 129; (2) in sCJD with PrP(Sc) type 2 (vs. PrP(Sc) type 1); and (3) in FFI versus sCJD or fCJD. Furthermore, truncated PrP(C) species were detected in sCJD and control samples without discernible differences. Finally, serine 43 of PrP(C) in the CSF and brain tissue from CJD patients showed more pronounced phosphorylation than in control donors.
Neurobiology of aging.Neurobiol Aging.2014 May;35(5):1177-88. doi: 10.1016/j.neurobiolaging.2013.11.010. Epub 2013 Nov 16.
The present study investigates whether posttranslational modifications of cellular prion protein (PrP(C)) in the cerebrospinal fluid (CSF) of humans with prion diseases are associated with methionine (M) and/or valine (V) polymorphism at codon 129 of the prion protein gene (PRNP), scrapie prion prot
PMID 24360565

Japanese Journal

Posttranslational regulation of microtubule-related molecules as a potential therapeutic target for neurodegeneration

Nakamura Kazuhiro
The Kitakanto medical journal = 北関東医学 63(3), 273-274, 2013-08-01
NAID 120005315278

〈Original Papers〉Gene cloning and characterization of pearl oyster Pinctada fucata α-tubulin

Miyashital Tomoyuki,Takami Akiko,Sugimoto Yui,Sakai Ayumi,Takagi Ryosuke
Memoirs of the Faculty of Biology-Oriented Science and Technology of Kinki University 31, 1-8, 2013-03
… The amino acid sequence of Pinctada fucata a-tubulin 2 contains the GGGTGSG domain that is a Guanosine triphosphate (GTP) nucleotide-binding site required for a-/I3-tubulin polymerization, and also contains putative posttranslational modification sites that are the phosphorylation residues at arginine (R) 79 and lysine (K) 336, and an acetylation residue at lysine (K) 40. …
NAID 120005260074

Label-Free Analysis of O-Glycosylation Site-Occupancy Based on the Signal Intensity of Glycopeptide/Peptide Ions

Wada Yoshinao
Mass spectrometry 1, A0008, 2012-12-01
… Mucin-type O-glycosylation is a major posttranslational modification of proteins. …
NAID 10031126345