| Primary Identifier | IPR016858 | Type | Family |
| Short Name | Hist_H4-K20_MeTrfase |
| description | Methyltransferases (EC 2.1.1.-) constitute an important class of enzymespresent in every life form. They transfer a methyl group most frequently fromS-adenosyl L-methionine (SAM or AdoMet) to a nucleophilic acceptor such asnitrogen, oxygen, sulfur or carbon leading to S-adenosyl-L-homocysteine(AdoHcy) and a methylated molecule. The substrates that are methylated bythese enzymes cover virtually every kind of biomolecules ranging from smallmolecules, to lipids, proteins and nucleic acids. Methyltransferases aretherefore involved in many essential cellular processes includingbiosynthesis, signal transduction, protein repair, chromatin regulation andgene silencing [, , ]. More than 230 different enzymatic reactions ofmethyltransferases have been described so far, of which more than 220 use SAMas the methyl donor [E1]. A review published in 2003 []divides allmethyltransferases into 5 classes based on the structure of their catalyticdomain (fold):class I: Rossmann-like alpha/beta class II: TIM beta/α-barrel alpha/beta class III: tetrapyrrole methylase alpha/betaclass IV: SPOUT alpha/beta class V: SET domainall betaA more recent paper []based on a study of the Saccharomyces cerevisiae methyltransferome argues for four more folds:class VI: transmembrane all alpha class VII: DNA/RNA-binding 3-helical bundle all alpha class VIII: SSo0622-like alpha+beta class IX: thymidylate synthetase alpha+betaThis entry represents the class V proteins, which contain the SET domain usually flanked byother domains forming the so-called pre- and post-SET regions. The enzymesbelonging to this class all N-methylate lysine in proteins. Most of them arehistone methyltransferases (EC 2.1.1.43) like the histone H3-K9methyltransferase dim-5 or the histone H3-K4methyltransferase SETD7 [, ]. Some others methylate thelarge subunit of the enzyme ribulose-bisphosphate-carboxylase/oxygenase(RuBisCO) (EC 2.1.1.127) in plants; in these enzymes the SET domain isinterrupted by a novel domain []. Cytochrome c lysine N-methyltransferases(EC 2.1.1.59) do not possess a SET domain, or at least not a SET domaindetected by any of the detection methods; however they do display a SET-likeregion and for this reason they are also assigned to this class []. |
