Amino Acids: Difference between revisions

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|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.