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Post-translational modification
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<h2 id="ptms-involving-addition-of-functional-groups">PTMs involving addition of functional groups</h2> <h3>Addition by an enzyme <i>in vivo</i></h3> <h4>Hydrophobic groups for membrane localization</h4> <ul><li><a href="/facts/Myristoylation/KbEstnBu">myristoylation</a> (a type of <a href="/facts/Acylation/9R8o69jN">acylation</a>), attachment of <a href="/facts/Myristate/INa6lUoj">myristate</a>, a C14 saturated acid</li> <li><a href="/facts/Palmitoylation/soDel1Xt">palmitoylation</a> (a type of acylation), attachment of <a href="/facts/Palmitate/wPvdsPHA">palmitate</a>, a C16 saturated acid</li> <li><a href="/facts/Isoprenylation/M8owTu4H">isoprenylation</a> or <a href="/facts/Prenylation/M8owTu4H">prenylation</a>, the addition of an <a href="/facts/Isoprenoid/1GvG7W7v">isoprenoid</a> group (e.g. <a href="/facts/Farnesol/0zWSo3Xq">farnesol</a> and <a href="/facts/Geranylgeraniol/SGw8L0sV">geranylgeraniol</a>) <ul><li><a href="/facts/Farnesylation/M8owTu4H">farnesylation</a></li> <li><a href="/facts/Geranylgeranylation/Q1SseuEm">geranylgeranylation</a></li></ul></li> <li><a href="/facts/Glypiation/hw97Xavu">glypiation</a>, <a href="/facts/GPI_anchor/dKsjvUTx">glycosylphosphatidylinositol (GPI) anchor</a> formation via an amide bond to C-terminal tail</li></ul> <h4>Cofactors for enhanced enzymatic activity</h4> <ul><li><a href="/facts/Lipoylation/9wTHHWBf">lipoylation</a> (a type of acylation), attachment of a <a href="/facts/Lipoate/9wTHHWBf">lipoate</a> (C8) functional group</li> <li><a href="/facts/Flavin_group/AKg5pskX">flavin</a> moiety (<a href="/facts/Flavin_mononucleotide/cWutCJmR">flavin mononucleotide</a> (FMN) or <a href="/facts/Flavin_adenine_dinucleotide/uzADx3ES">flavin adenine dinucleotide</a> (FAD)) may be covalently attached</li> <li><a href="/facts/Heme_C/u7WX9vRH">heme C</a> attachment via <a href="/facts/Thioether/GdyEz43f">thioether</a> bonds with <a href="/facts/Cysteine/kbqvUm6d">cysteines</a></li> <li><a href="/facts/Phosphopantetheinylation/hMKbgNWu">phosphopantetheinylation</a>, the addition of a 4'-phosphopantetheinyl moiety from <a href="/facts/Coenzyme_A/loAfeGpx">coenzyme A</a>, as in fatty acid, polyketide, non-ribosomal peptide and leucine biosynthesis</li> <li><a href="/facts/Retinylidene/h20jN8FC">retinylidene</a> <a href="/facts/Schiff_base/yg29UMLe">Schiff base</a> formation</li></ul> <h4>Modifications of translation factors</h4> <ul><li><a href="/facts/Diphthamide/2KSrXaNR">diphthamide</a> formation (on a histidine found in <a href="/facts/EEF2/dyEk0kuy">eEF2</a>)</li> <li>ethanolamine phosphoglycerol attachment (on glutamate found in <a href="/facts/Eukaryotic_translation_elongation_factor_1_alpha_1/9YvFgzGe">eEF1α</a>)<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a></li> <li><a href="/facts/Hypusine/fWbPcrJU">hypusine</a> formation (on conserved lysine of <a href="/facts/EIF5A/TngcLhQ0">eIF5A</a> (eukaryotic) and aIF5A (archaeal))</li> <li><a href="/facts/Beta-Lysine/vNxabl66">beta-Lysine</a> addition on a conserved lysine of the <a href="/facts/Elongation_factor_P/Asyhapqf">elongation factor P</a> (EFP) in most bacteria.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> EFP is a homolog to <a href="/facts/EIF5A/TngcLhQ0">eIF5A</a> (eukaryotic) and aIF5A (archaeal) (see above).</li></ul> <h4>Smaller chemical groups</h4> <ul><li><a href="/facts/Acylation/9R8o69jN">acylation</a>, e.g. <i>O</i>-acylation (<a href="/facts/Esters/FoUAIIw4">esters</a>), <i>N</i>-acylation (<a href="/facts/Amides/C6kCzYEA">amides</a>), <i>S</i>-acylation (<a href="/facts/Thioesters/UwfKqs1F">thioesters</a>) <ul><li><a href="/facts/Acetylation/PNMzRM4r">acetylation</a>, the addition of an <a href="/facts/Acetyl/rRmtXdn3">acetyl</a> group, either at the <a href="/facts/N-terminus/yKYpuaBJ">N-terminus</a> of the protein or at <a href="/facts/Lysine/CEetgA9L">lysine</a> residues.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> The reverse is called <a href="/facts/Deacetylation/PNMzRM4r">deacetylation</a>.</li> <li><a href="/facts/Formylation/y3TzFVza">formylation</a></li></ul></li> <li><a href="/facts/Alkylation/1rd5SNbt">alkylation</a>, the addition of an <a href="/facts/Alkyl/vmEk8X4v">alkyl</a> group, e.g. <a href="/facts/Methyl/fkM97EMD">methyl</a>, <a href="/facts/Ethyl_group/ydVhnBwD">ethyl</a> <ul><li><a href="/facts/Methylation/EvDMWVW5">methylation</a> the addition of a <a href="/facts/Methyl/fkM97EMD">methyl</a> group, usually at <a href="/facts/Lysine/CEetgA9L">lysine</a> or <a href="/facts/Arginine/y49Hdf1e">arginine</a> residues. The reverse is called <a href="/facts/Demethylation/AvM5BLjD">demethylation</a>.</li></ul></li> <li>amidation at C-terminus. Formed by oxidative dissociation of a C-terminal Gly residue.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a></li> <li><a href="/facts/Amide/C6kCzYEA">amide</a> bond formation <ul><li><a href="/facts/Amino_acid/WDxYwBny">amino acid</a> addition <ul><li>arginylation, a <a href="/facts/TRNA/pR9T5XSl">tRNA</a>-mediation addition</li> <li><a href="/facts/Polyglutamylation/WdedI98c">polyglutamylation</a>, covalent linkage of <a href="/facts/Glutamic_acid/7oXbNcvu">glutamic acid</a> residues to the N-terminus of tubulin and some other proteins.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> (See tubulin polyglutamylase)</li> <li><a href="/facts/Polyglycylation/kq9RXx15">polyglycylation</a>, covalent linkage of one to more than 40 <a href="/facts/Glycine/3nXI1hqW">glycine</a> residues to the <a href="/facts/Tubulin/j4Bk2wcL">tubulin</a> C-terminal tail</li></ul></li></ul></li> <li>butyrylation</li> <li><a href="/facts/Gamma-carboxylation/Fvk1Y3lg">gamma-carboxylation</a> dependent on <a href="/facts/Vitamin_K/dpTFSa4J">Vitamin K</a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a></li> <li><a href="/facts/Glycosylation/VYEeQCRz">glycosylation</a>, the addition of a <a href="/facts/Glycosyl/DP5dRJsp">glycosyl</a> group to either <a href="/facts/Arginine/y49Hdf1e">arginine</a>, <a href="/facts/Asparagine/KYIft5Jd">asparagine</a>, <a href="/facts/Cysteine/kbqvUm6d">cysteine</a>, <a href="/facts/Hydroxylysine/tdVRJ9IV">hydroxylysine</a>, <a href="/facts/Serine/4duVl30B">serine</a>, <a href="/facts/Threonine/7zffFQ6W">threonine</a>, <a href="/facts/Tyrosine/RJhEgE4C">tyrosine</a>, or <a href="/facts/Tryptophan/JcUxlxAh">tryptophan</a> resulting in a <a href="/facts/Glycoprotein/bKPzzW7m">glycoprotein</a>. Distinct from <a href="/facts/Glycation/3CHvekIg">glycation</a>, which is regarded as a nonenzymatic attachment of sugars. <ul><li><a href="/facts/O-GlcNAc/0DYsUnnd"><i>O</i>-GlcNAc</a>, addition of <i>N</i>-acetylglucosamine to serine or threonine residues in a β-glycosidic linkage</li> <li>polysialylation, addition of <a href="/facts/Polysialic_acid/aHTh4U0F">polysialic acid</a> (PSA) to <a href="/facts/Neural_cell_adhesion_molecule/AQAGclUp">neural cell adhesion molecule</a> (NCAM)</li></ul></li> <li>malonylation</li> <li><a href="/facts/Protein_hydroxylation/AevYpR6L">hydroxylation</a>: addition of an oxygen atom to the side-chain of a Pro or Lys residue</li> <li><a href="/facts/Iodination/vYrGVWcJ">iodination</a>: addition of an iodine atom to the aromatic ring of a tyrosine residue (e.g. in <a href="/facts/Thyroglobulin/whhQ9Dyb">thyroglobulin</a>)</li> <li><a href="/facts/ADP-ribosylation/rv6QqIqv">nucleotide addition</a> such as <a href="/facts/ADP-ribosylation/rv6QqIqv">ADP-ribosylation</a></li> <li><a href="/facts/Phosphate_ester/u4U9GS4z">phosphate ester</a> (<i>O</i>-linked) or <a href="/facts/Phosphoramidate/wqcYJvNd">phosphoramidate</a> (<i>N</i>-linked) formation <ul><li><a href="/facts/Phosphorylation/LXUEEeIL">phosphorylation</a>, the addition of a <a href="/facts/Phosphate/FDGVCxUG">phosphate</a> group, usually to <a href="/facts/Serine/4duVl30B">serine</a>, <a href="/facts/Threonine/7zffFQ6W">threonine</a>, and <a href="/facts/Tyrosine/RJhEgE4C">tyrosine</a> (<i>O</i>-linked), or <a href="/facts/Histidine/le7781NF">histidine</a> (<i>N</i>-linked)</li> <li><a href="/facts/Adenylylation/rWs3Co5P">adenylylation</a>, the addition of an <a href="/facts/Adenylyl/D9Ryfqad">adenylyl</a> moiety, usually to <a href="/facts/Tyrosine/RJhEgE4C">tyrosine</a> (<i>O</i>-linked), or <a href="/facts/Histidine/le7781NF">histidine</a> and <a href="/facts/Lysine/CEetgA9L">lysine</a> (<i>N</i>-linked)</li> <li>uridylylation, the addition of an uridylyl-group (i.e. <a href="/facts/Uridine_monophosphate/TkB63ofX">uridine monophosphate</a> (UMP)), usually to tyrosine</li></ul></li> <li><a href="/facts/Propionylation/ztNnhtFr">propionylation</a></li> <li><a href="/facts/Pyroglutamate/wh5pwznT">pyroglutamate</a> formation</li> <li><a href="/facts/S-glutathionylation/1EYTns60"><i>S</i>-glutathionylation</a></li> <li><a href="/facts/S-nitrosylation/Lcxa7IIu"><i>S</i>-nitrosylation</a></li> <li><i>S</i>-sulfenylation (<i>aka</i> <i>S</i>-sulphenylation), reversible covalent addition of one oxygen atom to the <a href="/facts/Thiol/VemKEDP9">thiol</a> group of a <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> residue<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a></li> <li><i>S</i>-sulfinylation, normally irreversible covalent addition of two oxygen atoms to the <a href="/facts/Thiol/VemKEDP9">thiol</a> group of a <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> residue<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li> <li><i>S</i>-sulfonylation, normally irreversible covalent addition of three oxygen atoms to the <a href="/facts/Thiol/VemKEDP9">thiol</a> group of a <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> residue, resulting in the formation of a <a href="/facts/Cysteic_acid/bdxHU2jF">cysteic acid</a> residue<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a></li> <li><a href="/facts/Succinylation/tvcq2yme">succinylation</a> addition of a <a href="/facts/Succinyl/v3KJqrQC">succinyl</a> group to <a href="/facts/Lysine/CEetgA9L">lysine</a></li> <li><a href="/facts/Tyrosine_sulfation/VCWUpWlx">sulfation</a>, the addition of a sulfate group to a <a href="/facts/Tyrosine/RJhEgE4C">tyrosine</a>.</li></ul> <h3>Non-enzymatic modifications <i>in vivo</i></h3> <p>Examples of non-enzymatic PTMs are glycation, glycoxidation, nitrosylation, oxidation, succination, and lipoxidation.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> </p> <ul><li><a href="/facts/Glycation/3CHvekIg">glycation</a>, the addition of a sugar molecule to a protein without the controlling action of an enzyme.</li> <li><a href="/facts/Carbamylation/up52qydJ">carbamylation</a> the addition of <a href="/facts/Isocyanic_acid/up52qydJ">Isocyanic acid</a> to a protein's N-terminus or the side-chain of Lys.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a></li> <li><a href="/facts/Carbonylation/Jq8jghNR">carbonylation</a> the addition of carbon monoxide to other organic/inorganic compounds.</li> <li>spontaneous <a href="/facts/Isopeptide_bond/tow46mFY">isopeptide bond</a> formation, as found in many surface proteins of <a href="/facts/Gram-positive_bacteria/H6WYQ17e">Gram-positive bacteria</a>.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a></li></ul> <h3>Non-enzymatic additions <i>in vitro</i></h3> <ul><li><a href="/facts/Biotinylation/LRwEYCKN">biotinylation</a>: covalent attachment of a biotin moiety using a biotinylation reagent, typically for the purpose of labeling a protein.</li> <li>carbamylation: the addition of isocyanic acid to a protein's N-terminus or the side-chain of Lys or Cys residues, typically resulting from exposure to urea solutions.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></li> <li>oxidation: addition of one or more oxygen atoms to a susceptible side-chain, principally of Met, Trp, His or Cys residues. Formation of <a href="/facts/Disulfide/eDx5Xtlg">disulfide</a> bonds between Cys residues.</li> <li><a href="/facts/Pegylation/SKK6XB02">pegylation</a>: covalent attachment of <a href="/facts/Polyethylene_glycol/tC7xBFwr">polyethylene glycol</a> (PEG) using a pegylation reagent, typically to the N-terminus or the side-chains of Lys residues. Pegylation is used to improve the efficacy of protein pharmaceuticals.</li></ul> <h2 id="conjugation-with-other-proteins-or-peptides">Conjugation with other proteins or peptides</h2> <ul><li><a href="/facts/Ubiquitin/hpulmU3m">ubiquitination</a>, the <a href="/facts/Covalent/EzMLf3Pz">covalent</a> linkage to the protein ubiquitin.</li> <li><a href="/facts/SUMOylation/T5vYKlQd">SUMOylation</a>, the covalent linkage to the <a href="/facts/SUMO_protein/T5vYKlQd">SUMO protein</a> (small ubiquitin-related modifier)<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></li> <li><a href="/facts/Neddylation/INuFfyfN">neddylation</a>, the covalent linkage to the <a href="/facts/NEDD8/Nsh14hjk">Nedd protein</a></li> <li>ISGylation, the covalent linkage to the <a href="/facts/ISG15/I8v5efu9">ISG15</a> protein (interferon-stimulated gene 15)<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></li> <li><a href="/facts/Pupylation/F6IFAPyy">pupylation</a>, the covalent linkage to the <a href="/facts/Prokaryotic_ubiquitin-like_protein/F6IFAPyy">prokaryotic ubiquitin-like protein</a></li></ul> <h2 id="chemical-modification-of-amino-acids">Chemical modification of amino acids</h2> <ul><li><a href="/facts/Citrullination/gsMUqv0n">citrullination</a>, or deimination, the conversion of <a href="/facts/Arginine/y49Hdf1e">arginine</a> to <a href="/facts/Citrulline/1X1LFYFG">citrulline</a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a></li> <li><a href="/facts/Deamidation/7lQjDhwT">deamidation</a>, the conversion of <a href="/facts/Glutamine/t94zX4SK">glutamine</a> to <a href="/facts/Glutamic_acid/7oXbNcvu">glutamic acid</a> or <a href="/facts/Asparagine/KYIft5Jd">asparagine</a> to <a href="/facts/Aspartic_acid/9DFSFPa1">aspartic acid</a></li> <li>eliminylation, the conversion to an <a href="/facts/Alkene/RtYcS6kU">alkene</a> by <a href="/facts/Elimination_reaction/7LSBwU3P">beta-elimination</a> of <a href="/facts/Phosphothreonine/7zffFQ6W">phosphothreonine</a> and <a href="/facts/Phosphoserine/nWq6mt9E">phosphoserine</a>, or <a href="/facts/Dehydration_reaction/dTAxlyRX">dehydration</a> of <a href="/facts/Threonine/7zffFQ6W">threonine</a> and <a href="/facts/Serine/4duVl30B">serine</a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li></ul> <h2 id="structural-changes">Structural changes</h2> <ul><li><a href="/facts/Disulfide_bridge/eDx5Xtlg">disulfide bridges</a>, the covalent linkage of two <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> amino acids</li> <li>lysine-cysteine bridges, the covalent linkage of 1 lysine and 1 or 2 cystine residues via an oxygen atom (NOS and SONOS bridges)<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a></li> <li><a href="/facts/Proteolytic_cleavage/G1ASdVat">proteolytic cleavage</a>, cleavage of a protein at a peptide bond</li> <li><a href="/facts/Isoaspartate/JqCjDgrj">isoaspartate</a> formation, via the cyclisation of asparagine or aspartic acid amino-acid residues</li> <li><a href="/facts/Racemization/t4C1SIXQ">racemization</a> <ul><li>of <a href="/facts/Serine/4duVl30B">serine</a> by <a href="/facts/Protein-serine_epimerase/TbgXq4RU">protein-serine epimerase</a></li> <li>of <a href="/facts/Alanine/fphQEdSc">alanine</a> in <a href="/facts/Dermorphin/vfV9QDQV">dermorphin</a>, a frog <a href="/facts/Opioid_peptide/FhQc0ntm">opioid peptide</a></li> <li>of <a href="/facts/Methionine/7neydPKo">methionine</a> in <a href="/facts/Deltorphin/6xFWLxI6">deltorphin</a>, also a frog opioid peptide</li></ul></li> <li><a href="/facts/Protein_splicing/n1sw2sbJ">protein splicing</a>, self-catalytic removal of <a href="/facts/Intein/n1sw2sbJ">inteins</a> analogous to mRNA processing</li></ul> <h2 id="statistics">Statistics</h2> <h3>Common PTMs by frequency</h3> <p>In 2011, statistics of each post-translational modification experimentally and putatively detected have been compiled using proteome-wide information from the Swiss-Prot database.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> The 10 most common experimentally found modifications were as follows:<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> </p> <table><tbody><tr><th>Frequency</th><th>Modification</th></tr><tr><td>58383</td><td><a href="/facts/Phosphorylation/LXUEEeIL">Phosphorylation</a></td></tr><tr><td>6751</td><td><a href="/facts/Acetylation/PNMzRM4r">Acetylation</a></td></tr><tr><td>5526</td><td><a href="/facts/N-linked_glycosylation/7W9cDU3q">N-linked glycosylation</a></td></tr><tr><td>2844</td><td>Amidation</td></tr><tr><td>1619</td><td><a href="/facts/Hydroxylation/AevYpR6L">Hydroxylation</a></td></tr><tr><td>1523</td><td><a href="/facts/Methylation/EvDMWVW5">Methylation</a></td></tr><tr><td>1133</td><td><a href="/facts/O-linked_glycosylation/9XfwdW5M">O-linked glycosylation</a></td></tr><tr><td>878</td><td><a href="/facts/Ubiquitin/hpulmU3m">Ubiquitylation</a></td></tr><tr><td>826</td><td><a href="/facts/Pyroglutamic_acid/wh5pwznT">Pyrrolidone carboxylic acid</a></td></tr><tr><td>504</td><td><a href="/facts/Sulfation/lI6B3Y1M">Sulfation</a></td></tr></tbody></table> <h3>Common PTMs by residue</h3> <p>Some common post-translational modifications to specific amino-acid residues are shown below. Modifications occur on the side-chain unless indicated otherwise. </p> <table><tbody><tr><th>Amino Acid</th><th>Abbrev.</th><th>Modification</th></tr><tr><th><a href="/facts/Alanine/fphQEdSc">Alanine</a></th><td>Ala or A</td><td><a href="/facts/Acetylation/PNMzRM4r">N-acetylation</a> (N-terminus)</td></tr><tr><th><a href="/facts/Arginine/y49Hdf1e">Arginine</a></th><td>Arg or R</td><td>deimination to <a href="/facts/Citrullination/gsMUqv0n">citrulline</a>, <a href="/facts/Protein_methylation/c5wJoSq6">methylation</a></td></tr><tr><th><a href="/facts/Asparagine/KYIft5Jd">Asparagine</a></th><td>Asn or N</td><td><a href="/facts/Deamidation/7lQjDhwT">deamidation</a> to Asp or iso(Asp), <a href="/facts/N-linked_glycosylation/7W9cDU3q">N-linked glycosylation</a>, <a href="/facts/Isopeptide_bond/tow46mFY">spontaneous isopeptide bond formation</a></td></tr><tr><th><a href="/facts/Aspartic_acid/9DFSFPa1">Aspartic acid</a></th><td>Asp or D</td><td><a href="/facts/Deamidation/7lQjDhwT">isomerization</a> to isoaspartic acid, spontaneous isopeptide bond formation</td></tr><tr><th><a href="/facts/Cysteine/kbqvUm6d">Cysteine</a></th><td>Cys or C</td><td><a href="/facts/Disulfide/eDx5Xtlg">disulfide</a>-bond formation, oxidation to sulfenic, sulfinic or sulfonic acid, <a href="/facts/Palmitoylation/soDel1Xt">palmitoylation</a>, N-acetylation (N-terminus), <a href="/facts/S-nitrosylation/Lcxa7IIu">S-nitrosylation</a></td></tr><tr><th><a href="/facts/Glutamine/t94zX4SK">Glutamine</a></th><td>Gln or Q</td><td>cyclization to <a href="/facts/Pyroglutamic_acid/wh5pwznT">pyroglutamic acid</a> (N-terminus), deamidation to <a href="/facts/Glutamic_acid/7oXbNcvu">glutamic acid</a> or <a href="/facts/Isopeptide_bond/tow46mFY">isopeptide bond</a> formation to a <a href="/facts/Lysine/CEetgA9L">lysine</a> by a <a href="/facts/Transglutaminase/8fjQq01V">transglutaminase</a></td></tr><tr><th><a href="/facts/Glutamic_acid/7oXbNcvu">Glutamic acid</a></th><td>Glu or E</td><td>cyclization to <a href="/facts/Pyroglutamic_acid/wh5pwznT">pyroglutamic acid</a> (N-terminus), <a href="/facts/Gamma-carboxylation/Fvk1Y3lg">gamma-carboxylation</a></td></tr><tr><th><a href="/facts/Glycine/3nXI1hqW">Glycine</a></th><td>Gly or G</td><td>N-<a href="/facts/Myristoylation/KbEstnBu">myristoylation</a> (N-terminus), N-acetylation (N-terminus)</td></tr><tr><th><a href="/facts/Histidine/le7781NF">Histidine</a></th><td>His or H</td><td><a href="/facts/Histidine_kinase/pkjn8bku">phosphorylation</a></td></tr><tr><th><a href="/facts/Isoleucine/sJW4dxnh">Isoleucine</a></th><td>Ile or I</td><td></td></tr><tr><th><a href="/facts/Leucine/X7YrkvA5">Leucine</a></th><td>Leu or L</td><td></td></tr><tr><th><a href="/facts/Lysine/CEetgA9L">Lysine</a></th><td>Lys or K</td><td><a href="/facts/Acetylation/PNMzRM4r">acetylation</a>, <a href="/facts/Ubiquitylation/hpulmU3m">ubiquitylation</a>, <a href="/facts/SUMO_protein/T5vYKlQd">SUMOylation</a>, <a href="/facts/Protein_methylation/c5wJoSq6">methylation</a>, <a href="/facts/Hydroxylation/AevYpR6L">hydroxylation</a> leading to <a href="/facts/Allysine/CSommfte">allysine</a>, spontaneous isopeptide bond formation</td></tr><tr><th><a href="/facts/Methionine/7neydPKo">Methionine</a></th><td>Met or M</td><td>N-acetylation (N-terminus), N-linked ubiquitination, oxidation to <a href="/facts/Sulfoxide/Stk3Vnj9">sulfoxide</a> or <a href="/facts/Sulfone/LJLP1RcT">sulfone</a></td></tr><tr><th><a href="/facts/Phenylalanine/eyojfW7t">Phenylalanine</a></th><td>Phe or F</td><td></td></tr><tr><th><a href="/facts/Proline/x1ABSW5A">Proline</a></th><td>Pro or P</td><td><a href="/facts/Hydroxylation/AevYpR6L">hydroxylation</a></td></tr><tr><th><a href="/facts/Serine/4duVl30B">Serine</a></th><td>Ser or S</td><td><a href="/facts/Phosphorylation/LXUEEeIL">phosphorylation</a>, <a href="/facts/O-linked_glycosylation/9XfwdW5M">O-linked glycosylation</a>, N-acetylation (N-terminus)</td></tr><tr><th><a href="/facts/Threonine/7zffFQ6W">Threonine</a></th><td>Thr or T</td><td>phosphorylation, O-linked glycosylation, N-acetylation (N-terminus)</td></tr><tr><th><a href="/facts/Tryptophan/JcUxlxAh">Tryptophan</a></th><td>Trp or W</td><td>mono- or di-oxidation, formation of <a href="/facts/Kynurenine/Y4q8E7md">kynurenine</a>, <a href="/facts/Tryptophan_tryptophylquinone/7MjpWSXy">tryptophan tryptophylquinone</a></td></tr><tr><th><a href="/facts/Tyrosine/RJhEgE4C">Tyrosine</a></th><td>Tyr or Y</td><td><a href="/facts/Tyrosine_sulfation/VCWUpWlx">sulfation</a>, phosphorylation</td></tr><tr><th><a href="/facts/Valine/uTMLXBG4">Valine</a></th><td>Val or V</td><td>N-acetylation (N-terminus)</td></tr></tbody></table> <h2 id="databases-and-tools">Databases and tools</h2> <p>Protein sequences contain sequence motifs that are recognized by modifying enzymes, and which can be documented or predicted in PTM databases. With the large number of different modifications being discovered, there is a need to document this sort of information in databases. PTM information can be collected through experimental means or predicted from high-quality, manually curated data. Numerous databases have been created, often with a focus on certain taxonomic groups (e.g. human proteins) or other features. </p> <h3>List of resources</h3> <ul><li><a href="http://www.phosphosite.org/">PhosphoSitePlus</a><a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> – A database of comprehensive information and tools for the study of mammalian protein post-translational modification</li> <li>ProteomeScout<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> – A database of proteins and post-translational modifications experimentally</li> <li><a href="/facts/Human_Protein_Reference_Database/6zBaACvD">Human Protein Reference Database</a><a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> – A database for different modifications and understand different proteins, their class, and function/process related to disease causing proteins</li> <li><a href="/facts/PROSITE/TcqJLVBc">PROSITE</a><a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> – A database of Consensus patterns for many types of PTM's including sites</li> <li><a href="/facts/Protein_Information_Resource/wHD5WbCB">RESID</a><a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> – A database consisting of a collection of annotations and structures for PTMs.</li> <li><a href="https://research.bioinformatics.udel.edu/iptmnet/">iPTMnet</a> <a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a>– A database that integrates PTM information from several knowledgbases and text mining results.</li> <li>dbPTM<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a> – A database that shows different PTM's and information regarding their chemical components/structures and a frequency for amino acid modified site</li> <li><a href="https://www.uniprot.org/help/post-translational_modification">Uniprot</a> has PTM information although that may be less comprehensive than in more specialized databases.</li> <li><a href="https://www.oglcnac.mcw.edu/">The <i>O</i>-GlcNAc Database</a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a><a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> - A curated database for protein O-GlcNAcylation and referencing more than 14 000 protein entries and 10 000 <i>O</i>-GlcNAc sites.</li></ul> <h3>Tools</h3> <p>List of software for visualization of proteins and their PTMs </p> <ul><li><a href="/facts/PyMOL/SbMJ9lPl">PyMOL</a><a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a> – introduce a set of common PTM's into protein models</li> <li>AWESOME<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a> – Interactive tool to see the role of single nucleotide polymorphisms to PTM's</li> <li><a href="/facts/UCSF_Chimera/x4JpEHlH">Chimera</a><a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> – Interactive Database to visualize molecules</li></ul> <h2 id="case-examples">Case examples</h2> <ul><li>Cleavage and formation of <a href="/facts/Disulfide_bridge/eDx5Xtlg">disulfide bridges</a> during the production of <a href="/facts/Insulin/oXG0myt1">insulin</a></li> <li>PTM of <a href="/facts/Histone/krb5VJfp">histones</a> as regulation of <a href="/facts/Transcription_(genetics)/bDgp9HDN">transcription</a>: <a href="/facts/RNA_polymerase_control_by_chromatin_structure/MK2kgybw">RNA polymerase control by chromatin structure</a></li> <li>PTM of <a href="/facts/RNA_polymerase_II/MK2kgybw">RNA polymerase II</a> as regulation of transcription</li> <li>Cleavage of polypeptide chains as crucial for lectin specificity<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a></li> <li>Influence of Ni(II) in the Acetylation of Histones H4 Protein <a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a></li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Protein_targeting/R3B37xMM">Protein targeting</a></li> <li><a href="/facts/Post-translational_regulation/nr8MhB1s">Post-translational regulation</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://ftp.uniprot.org/pub/databases/uniprot/current_release/knowledgebase/complete/docs/ptmlist.txt">Controlled vocabulary of post-translational modifications</a> in <a href="/facts/Uniprot/lfDDHjAl">Uniprot</a></li> <li><a href="https://www.uniprot.org/docs/ptmlist">List of posttranslational modifications in ExPASy</a></li> <li><a href="http://supfam.org/SUPERFAMILY/cgi-bin/dcbo.cgi?type=KW;po=9991">Browse SCOP domains by PTM</a> — from the <a href="/facts/DcGO/mFELnzst">dcGO</a> database</li> <li><a href="http://www.cytoskeleton.com/about-signal-seeker-ptm-detection">Overview and description of commonly used post-translational modification detection techniques</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Pratt, Charlotte W.; Voet, Judith G.; Voet, Donald (2006). 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