Methylation in bacterial ribosome biogenesis and function - how, when and why?

Ribosomal RNA (rRNA) is posttranscriptionally modified during ribosome biogenesis in all of life.

In bacteria, the most common modification is methylation, added by site-specific methyltransferases (MTases) that use SAM as methyl donor.

Antibiotic-resistance MTases similarly add methylations that sterically protect bacterial ribosomes from antibiotic binding and inhibition.Here, we first aim to to clarify how MTases recognize and methylate short-lived structural states of rRNA during E. coli ribosome biogenesis.

We will use adduct-forming SAM analogues, cryo-EM and crystallography to capture and visualize MTase complexes with different ribosomal precursors, and fluorescence microscopy to monitor the time that MTases spend bound to ribosomal precursors in living E. coli.Second, we aim to elucidate how the cumulative effect of SAM-mediated rRNA methylation contributes to robustness of ribosome structure and function.

This will be addressed through cryo-EM and biochemistry of ribosomes from E. coli knockout strains lacking one or several modifications.

The project will involve two structural-biology postdocs and collaborators in chemistry, fluorescence microscopy and ribosome biochemistry.The results will provide new insights into the ribosome, one of the most central machineries in all life. It may also provide starting points for design of new antibiotics that target ribosome assembly.