{{Infobox protein family | Symbol = PIN | Name = PIN domain | image = PDB_1o4w_EBI.jpg | width = 250 | caption = Crystal structure of PIN (PilT N-terminus) domain (AF0591) from Archaeoglobus fulgidus at 1.90 Angstrom resolution. {{PDB2|1o4w}} | Pfam = PF01850 | InterPro = IPR002716 | SMART = CBS | PROSITE = | SCOP = 3dbo | TCDB = | OPM family = | OPM protein = | CDD = cd09852 | PDB = {{PDB2|3dbo}}, {{PDB2|1v8o}}, {{PDB2|1o4w}} }}
In molecular biology the '''PIN domain''' is a protein domain that is about 130 amino acids in length. PIN domains function as nuclease enzymes that cleave single stranded RNA in a sequence- or structure-dependent manner.<ref name="pmid21036780">{{cite journal | vauthors = Arcus VL, McKenzie JL, Robson J, Cook GM | title = The PIN-domain ribonucleases and the prokaryotic VapBC toxin-antitoxin array | journal = Protein Engineering, Design & Selection | volume = 24 | issue = 1–2 | pages = 33–40 | date = January 2011 | pmid = 21036780 | doi = 10.1093/protein/gzq081 | doi-access = free }}</ref><ref name=":0" />
PIN domains contain four nearly invariant acidic residues.<ref name=":0" /> Crystal structures show these residues clustered together in the putative active site. In eukaryotes PIN domains are found in proteins involved in nonsense mediated mRNA decay, in proteins such as SMG5 and SMG6, and in processing of 18S ribosomal RNA. The majority of PIN-domain proteins found in prokaryotes are the toxic components of toxin-antitoxin operons.<ref name=":0">{{cite journal | vauthors = Matelska D, Steczkiewicz K, Ginalski K | title = Comprehensive classification of the PIN domain-like superfamily | journal = Nucleic Acids Research | volume = 45 | issue = 12 | pages = 6995–7020 | date = July 2017 | pmid = 28575517 | pmc = 5499597 | doi = 10.1093/nar/gkx494 }}</ref> These loci provide a control mechanism that helps free-living prokaryotes cope with nutritional stress.<ref name="pmid15864262">{{cite journal | vauthors = Gerdes K, Christensen SK, Løbner-Olesen A | title = Prokaryotic toxin-antitoxin stress response loci | journal = Nature Reviews. Microbiology | volume = 3 | issue = 5 | pages = 371–82 | date = May 2005 | pmid = 15864262 | doi = 10.1038/nrmicro1147 | s2cid = 13417307 }}</ref>
== References ==
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Category:Protein domains