Structural highlights
Function[MCE_MIMIV] Responsible for methylating the 5'-cap structure of mRNAs. Publication Abstract from PubMedThe RNA triphosphatase (RTPase) components of the mRNA capping apparatus are a bellwether of eukaryal taxonomy. Fungal and protozoal RTPases belong to the triphosphate tunnel metalloenzyme (TTM) family, exemplified by yeast Cet1. Several large DNA viruses encode metal-dependent RTPases unrelated to the cysteinyl-phosphatase RTPases of their metazoan host organisms. The origins of DNA virus RTPases are unclear because they are structurally uncharacterized. Mimivirus, a giant virus of amoeba, resembles poxviruses in having a trifunctional capping enzyme composed of a metal-dependent RTPase module fused to guanylyltransferase (GTase) and guanine-N7 methyltransferase domains. The crystal structure of mimivirus RTPase reveals a minimized tunnel fold and an active site strikingly similar to that of Cet1. Unlike homodimeric fungal RTPases, mimivirus RTPase is a monomer. The mimivirus TTM-type RTPase-GTase fusion resembles the capping enzymes of amoebae, providing evidence that the ancestral large DNA virus acquired its capping enzyme from a unicellular host. Characterization of a trifunctional mimivirus mRNA capping enzyme and crystal structure of the RNA triphosphatase domain.,Benarroch D, Smith P, Shuman S Structure. 2008 Apr;16(4):501-12. PMID:18400173[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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