RNA triphosphatase

In molecular biology, RNA 5'-triphosphatases (RTPases) are phosphatases that cleave the 5'-terminal γ-β phosphoanhydride bond of nascent messenger RNA molecules, enabling the addition of a five-prime cap as part of post-transcriptional modifications. RTPases generate 5'-diphosphate-ended mRNA and a phosphate ion from 5'-triphosphate-ended precursor mRNA. mRNA guanylyltransferase then adds a backwards guanosine monophosphate (GMP) group from GTP, generating pyrophosphate, and mRNA (guanine-N7-)-methyltransferase methylates the guanine to form the final 5'-cap structure.