Y Xue

Picture an old house where every room ages in its own way: in one, the wallpaper has faded; in another, the floorboards creak; and in a third, everything looks brand new. The brain ages much the same way: different cell types accumulate changes at different rates, and until recently we had no tool to peer into each "room" and measure its age separately.

In the workshop where ribosomes are assembled, the molecular tailor YbeY stitches an extra link into the protein chain of uS11. That link is isoaspartate, an amino acid whose backbone is one methylene group longer. The insertion makes the protein slightly longer, and it settles more tightly into the ribosome's framework.