Domain

RNA 3'-terminal phosphate cyclase domain (IPR023797)

Short name: RNA3'_phos_cyclase_dom

Domain relationships

None.

Description

RNA cyclases are a family of RNA-modifying enzymes that are conserved in eukaryotes, bacteria and archaea. Type 1 RNA 3'-terminal phosphate cyclases (EC:6.5.1.4) [PMID: 9184239, PMID: 2199762] catalyse the conversion of 3'-phosphate to a 2',3'-cyclic phosphodiester at the end of RNA:

ATP + RNA 3'-terminal-phosphate = AMP + diphosphate + RNA terminal-2',3'-cyclic-phosphate

The physiological function of the cyclase is not known, but the enzyme could be involved in the maintenance of cyclic ends in tRNA splicing intermediates or in the cyclisation of the 3' end of U6 snRNA [PMID: 9184239].

A second subfamily of RNA 3'-terminal phosphate cyclases (type 2) that do not have cyclase activity have been identified in eukaryotes. They are localised to the nucleolus and are involved in ribosomal modification [PMID: 10790377].

The crystal structure of RNA 3'-terminal phosphate cyclase shows that each molecule consists of two domains. The larger domain contains three repeats of a folding unit comprising two parallel alpha helices and a four-stranded beta sheet; this fold was previously identified in translation initiation factor 3 (IF3). The large domain is similar to one of the two domains of 5-enolpyruvylshikimate-3-phosphate synthase and UDP-N-acetylglucosamine enolpyruvyl transferase. The smaller domain uses a similar secondary structure element with different topology, observed in many other proteins such as thioredoxin [PMID: 10673421]. Although the active site of this enzyme has not been unambiguously assigned, it can be mapped to a region surrounding His309, an adenylate acceptor, in which a number of amino acids are highly conserved in the enzyme from different sources [PMID: 10673421].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam