Editing Polymerase (section)

== By structure ==
Polymerases are generally split into two superfamilies, the "right hand" fold ({{InterPro|IPR043502}}) and the "double psi [[beta barrel]]" (often simply "double-barrel") fold. The former is seen in almost all DNA polymerases and almost all viral single-subunit polymerases; they are marked by a conserved "palm" domain.<ref name="pmid9309225">{{cite journal | vauthors = Hansen JL, Long AM, Schultz SC | title = Structure of the RNA-dependent RNA polymerase of poliovirus | journal = Structure | volume = 5 | issue = 8 | pages = 1109–22 | date = August 1997 | pmid = 9309225 | doi = 10.1016/S0969-2126(97)00261-X | doi-access = free }}</ref> The latter is seen in all multi-subunit RNA polymerases, in cRdRP, and in "family D" DNA polymerases found in archaea.<ref name="pmid11839495">{{cite journal | vauthors = Cramer P | title = Multisubunit RNA polymerases | journal = Current Opinion in Structural Biology | volume = 12 | issue = 1 | pages = 89–97 | date = February 2002 | pmid = 11839495 | doi = 10.1016/S0959-440X(02)00294-4 }}</ref><ref name=qde1-mono>{{cite journal | vauthors = Sauguet L | title = The Extended "Two-Barrel" Polymerases Superfamily: Structure, Function and Evolution | journal = Journal of Molecular Biology | volume = 431 | issue = 20 | pages = 4167–4183 | date = September 2019 | pmid = 31103775 | doi = 10.1016/j.jmb.2019.05.017 | doi-access = free }}</ref> The "X" family represented by [[DNA polymerase beta]] has only a vague "palm" shape, and is sometimes considered a different superfamily ({{InterPro|IPR043519}}).<ref>{{cite journal | vauthors = Salgado PS, Koivunen MR, Makeyev EV, Bamford DH, Stuart DI, Grimes JM | title = The structure of an RNAi polymerase links RNA silencing and transcription | journal = PLoS Biology | volume = 4 | issue = 12 | pages = e434 | date = December 2006 | pmid = 17147473 |  pmc=1750930 | doi = 10.1371/journal.pbio.0040434 | doi-access = free }}</ref>

Primases generally don't fall into either category. Bacterial primases usually have the Toprim domain, and are related to [[topoisomerase]]s and mitochondrial helicase [[Twinkle (protein)|twinkle]].<ref>{{cite journal | vauthors = Aravind L, Leipe DD, Koonin EV | title = Toprim--a conserved catalytic domain in type IA and II topoisomerases, DnaG-type primases, OLD family nucleases and RecR proteins | journal = Nucleic Acids Research | volume = 26 | issue = 18 | pages = 4205–13 | date = September 1998 | pmid = 9722641 | pmc = 147817 | doi = 10.1093/nar/26.18.4205 }}</ref> Archae and eukaryotic primases form an unrelated AEP family, possibly related to the polymerase palm. Both families nevertheless associate to the same set of helicases.<ref>{{cite journal | vauthors = Iyer LM, Koonin EV, Leipe DD, Aravind L | title = Origin and evolution of the archaeo-eukaryotic primase superfamily and related palm-domain proteins: structural insights and new members | journal = Nucleic Acids Research | volume = 33 | issue = 12 | pages = 3875–96 | date = 2005 | pmid = 16027112 | pmc = 1176014 | doi = 10.1093/nar/gki702 }}</ref>

<gallery>
File:WikiHandDNAPolII.png|Right hand structure of Bacteriophage RB69, a family B DdRP.
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