Speaker Calendar » 2017 Selmer
Ribosomes are central players in all cells, translating mRNA into protein. Ribosome biogenesis in all species involves post-transcriptional modifications of rRNA. In Escherichia coli, a site-specific enzyme adds each modification and the most frequent type is nucleotide methylation of N, O or C atoms. Although the cell invests a lot in its rRNA modification machinery, the role of most modifications remains unknown and little is known about how these enzymes recognize their substrates.
We have structurally and functionally characterized two AdoMet-dependent 23S rRNA MTases that act during the early stages of ribosome assembly in E. coli. RlmM methylates the 2'O ribose of C2498 and RlmJ methylates the exocyclic N6 of A2030, both located close to the peptidyl transferase center in the mature 50S subunit. Crystal structures and biochemical experiments elucidate how these enzymes each use re-occuring catalytic domains in combination with dedicated target recognition domains to each recognize and modify one specific RNA nucleotide.