Reaction: GTP + [RNA]-3'-(3'-phospho-ribonucleoside) = GMP + diphosphate + [RNA]-3'-(2',3'-cyclophospho)-ribonucleoside (overall reaction)
(1a) GTP + [RNA 3'-phosphate cyclase]-L-histidine = 5'-guanosyl [RNA 3'-phosphate cyclase]-Nτ-phosphono-L-histidine + diphosphate
(1b) 5'-guanosyl [RNA 3'-phosphate cyclase]-Nτ-phosphono-L-histidine + [RNA]-3'-(3'-phospho-ribonucleoside) = [RNA 3'-phosphate cyclase]-L-histidine + [RNA]-3'-ribonucleoside-3'-(5'-diphosphoguanosine)
(1c) [RNA]-3'-ribonucleoside-3'-(5'-diphosphoguanosine) = [RNA]-3'-(2',3'-cyclophospho)-ribonucleoside + GMP
Other name(s): Pf-Rtc; RNA-3'-phosphate cyclase (GTP)
Systematic name: RNA-3'-phosphate:RNA ligase (cyclizing, GMP-forming)
Comments: The enzyme, which is specific for GTP, was characterized from the archaeon Pyrococcus furiosus. The enzyme converts the 3'-terminal phosphate of various RNA substrates into the 2',3'-cyclic phosphodiester in a GTP-dependent reaction. Catalysis occurs by a three-step mechanism, starting with the activation of the enzyme by GTP, forming a phosphoramide bond between guanylate and a histidine residue. The guanylate group is then transferred to the 3'-phosphate terminus of the substrate, forming the capped structure [RNA]-3'-(5'-diphosphoguanosine). Finally, the enzyme catalyses an attack of the vicinal O2' on the 3'-phosphorus, which results in formation of cyclic phosphate and release of the guanylate. cf. EC 6.5.1.4, RNA-3'-phosphate cyclase (ATP).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Sato, A., Soga, T., Igarashi, K., Takesue, K., Tomita, M. and Kanai, A. GTP-dependent RNA 3'-terminal phosphate cyclase from the hyperthermophilic archaeon Pyrococcus furiosus. Genes Cells 16 (2011) 1190-1199. [PMID: 22074260]