More than 70 different methylated nucleotides play important functional roles in present-day RNA. Mostly known for shaping the structures and tuning the functions of non-coding rRNA, tRNA, and snRNA, some modifications also influence gene expression programmes by regulating the fate and function of mRNA. The majority of methylated nucleotides currently known in RNA are installed by post-synthetic (i.e., post- or co-transcriptional) methylation by protein enzymes that use S-adenosylmethionine (SAM) as the universal methyl group donor. Methyl transferases are considered ancient enzymes, and methylated nucleotides are also discussed as molecular fossils of the early Earth produced by prebiotic methylating agents. In an era preceding modern life based on DNA and proteins, RNA was thought to function both as primary genetic material and as catalyst.11 Ribozymes have been discovered in Nature, where they catalyse RNA cleavage and ligation reactions, mostly in the context of RNA splicing and retrotransposition. In vitro selected ribozymes have been evolved as RNA ligases and replicases that are able to reproduce themselves or their ancestors, and are able to produce functional RNAs, including ribozymes and aptamers. Self-alkylating ribozymes have been described using reactive iodo- or chloroacetyl derivatives,18–20 or electrophilic epoxides, but the design of earlier in vitro selection strategies prevented the emergence of catalysts capable of transferring a one-carbon unit. Thus, ribozymes that catalyse RNA methylation have so far remained elusive. Here you can see a crystal structure of a SAM-dependent methyltransferase ribozyme (PDB code: 7DWH)
#molecularart ... #immolecular ... #ribozyme .. #RNA ... #methyltransferase ... #SAMET ... #xray
Structure rendered with @proteinimaging and depicted with @corelphotopaint
#molecularart ... #immolecular ... #ribozyme .. #RNA ... #methyltransferase ... #SAMET ... #xray
Structure rendered with @proteinimaging and depicted with @corelphotopaint
