The ribosome is a tiny factory that assembles proteins in every cell. One of its proteins, uS11, carries an unusual modification in all living things: an extra link, isoaspartate, is stitched into its chain. This link makes the protein slightly longer, and it sits more tightly in the ribosome's framework. Previously, such a transformation was considered a random defect. But in uS11 it is always present and always in the same spot.
The question was speed. E. coli divides every 20 minutes, while a spontaneous insertion of the link takes about a day and a half. So the cell needs an accelerator. The authors of the study found it: the enzyme YbeY. It works like a tailor who quickly stitches an extra link into the protein chain.
When the ybeY gene was removed from the bacterium, the ribosomes became worse at holding another protein, bS21. Such ribosomes assembled poorly and translated RNA into protein at only 30% of the normal rate. So the extra link is not a defect but an important detail. Understanding how YbeY works could help create antibiotics: this enzyme is present in bacteria but absent in human cytoplasm.
The spontaneous conversion of asparagine to isoaspartate in a peptide with the Asn-Gly motif has a half-life of about 1.2 days, but YbeY speeds this reaction up to minutes, which is necessary for assembling the ribosome within the E. coli cell cycle (about 20 minutes).
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.