Amino Acids: Difference between revisions

← Older edit Newer edit →

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Eric Martz, Andrea Gorrell, Angel Herraez, Joel L. Sussman

@@ Line 89: / Line 89: @@
 ==Unusual Amino Acids==
-Many post-translational modifications of amino acids occur, including phosphorylation of serine, threonine, or tyrosine, and nitrosylation, e.g. to produce [[nitrotyrosine]]. There are at least two non-standard amino acids that are [http://en.wikipedia.org/wiki/Genetic_code genetically encoded], discussed below. In 2014, the [[PDB]] is in the process of adding these two to make 22 standard amino acids.
+There are at least two non-standard amino acids that are [http://en.wikipedia.org/wiki/Genetic_code genetically encoded], discussed below. In 2014, the [[PDB]] is in the process of adding these two to make 22 standard amino acids.
 ===Selenocysteine: the 21st amino acid===
-Rare proteins in all domains of life include '''[[Selenocysteine|selenocysteine (Sec, U)]]''', designated the 21st amino acid<ref name='21st'>PMID: 11028985</ref>. Over a dozen entries in the [[PDB]] include selenocysteine, identified as CSE.
+Rare proteins in all domains of life include '''[[Selenocysteine|selenocysteine (Sec, U)]]''', designated the 21st amino acid<ref name='21st'>PMID: 11028985</ref>. Over [http://www.rcsb.org/pdb/ligand/ligandsummary.do?hetId=SEC 38 entries] in the [[PDB]] include selenocysteine, identified as SEC.
 ===Pyrrolysine: the 22nd amino acid===
-'''[[Pyrrolysine|pyrrolysine (Pyl, O)]]'''<ref>See [http://en.wikipedia.org/wiki/Pyrrolysine Pyrrolysine in Wikipedia].</ref> is a genetically encoded amino acid that occurs naturally in methanogenic archaea, sometimes called the 22nd amino acid<ref>PMID: 15380192</ref>. It occurs in [[Pyrrolysine|several entries]] in the PDB.
+'''[[Pyrrolysine|pyrrolysine (Pyl, O)]]'''<ref>See [http://en.wikipedia.org/wiki/Pyrrolysine Pyrrolysine in Wikipedia].</ref> is a genetically encoded amino acid that occurs naturally in methanogenic archaea, sometimes called the 22nd amino acid<ref>PMID: 15380192</ref>. It occurs in [http://www.rcsb.org/pdb/ligand/ligandsummary.do?hetId=PYL several entries] in the PDB.
+See [[Pyrrolysine|more details]].
+<!--
 Editor's note: Contributions here by [[User:Andrea Gorrell]] were moved to the page on [[Pyrrolysine]].
+-->
 ===No 23rd amino acid?===
 The 21st and 22nd amino acids are specified by the [http://en.wikipedia.org/wiki/Genetic_code stop codons UGA and UAG] respectively, modified with downstream stem-loop structures in the mRNA.
 Lobanov ''et al.''<ref name='23rd'>PMID: 16713651</ref> searched "16 archaeal and 130 bacterial genomes for tRNAs with anticodons corresponding to the three stop signals". Their data suggest that "the occurrence of additional amino acids that are widely distributed and genetically encoded is unlikely."
+===Postranslational modifications===
+Many unusual amino acids are formed by enzyme-catalyzed reactions that modify a standard amino acid after it has been included in a polypeptide; these are called post-translational modifications. Among them:
+* phosphorylation of serine, threonine, or tyrosine
+* hydroxylation of proline (to yield hydroxyproline, e.g. in [[collagen]])
+* acetylation of lysine or the N terminus
+* methylation of lysine
+* carboxylation of aspartate or glutamate
+* nitrosylation, e.g. to produce [[nitrotyrosine]]
+* acylation with a fatty acid
+* prenylation
+* glycosylation of serine, threonine or asparagine (yielding glycoproteins)
 ==Structure, Properties, Behaviors in Proteins==