EC Explorer

6.5.1.4

RNA 3′-terminal-phosphate cyclase (ATP)

ATP + [RNA]-3′-(3′-phospho-ribonucleoside) = AMP + diphosphate + [RNA]-3′-(2′,3′-cyclophospho)-ribonucleoside (overall reaction);;(1a) ATP + [RNA 3′-phosphate cyclase]-L-histidine = [RNA 3′-phosphate cyclase]-N^τ-(5′-adenylyl)-L-histidine + diphosphate;;(1b) [RNA 3′-phosphate cyclase]-N^τ-(5′-adenylyl)-L-histidine + [RNA]-3′-(3′-phospho-ribonucleoside) = [RNA 3′-phosphate cyclase]-L-histidine + [RNA]-3′-ribonucleoside-3′-(5′-diphosphoadenosine);;(1c) [RNA]-3′-ribonucleoside-3′-(5′-diphosphoadenosine) = [RNA]-3′-(2′,3′-cyclophospho)-ribonucleoside + AMP

rtcA (gene name), RNA cyclase (ambiguous), RNA-3′-phosphate cyclase (ambiguous)

RNA-3′-phosphate:RNA ligase (cyclizing, AMP-forming)

85638-41-1

The enzyme converts the 3′-terminal phosphate of various RNA substrates into the 2′,3′-cyclic phosphodiester in an ATP-dependent reaction. Catalysis occurs by a three-step mechanism, starting with the activation of the enzyme by ATP, forming a phosphoramide bond between adenylate and a histidine residue [5,6]. The adenylate group is then transferred to the 3′-phosphate terminus of the substrate, forming the capped structure [RNA]-3′-(5′-diphosphoadenosine). Finally, the enzyme catalyses an attack of the vicinal O-2′ on the 3′-phosphorus, which results in formation of cyclic phosphate and release of the adenylate. The enzyme also has a polynucleotide 5′ adenylylation activity [7]. cf. EC 6.5.1.5, RNA 3′-terminal-phosphate cyclase (GTP).

created 1986, modified 1989, modified 2013, modified 2016