Protein aggregates are deemed to be one reason for the death of nerve cells in disorders such as Alzheimer’s or Huntington’s disease. As researchers at the Max Planck Institute of Biochemistry report in the current issue of Nature, they have now decoded a new cellular mechanism for the development of aggregates. Missing stop signals in the production of proteins lead erroneously to long lysine chains at the end of the protein. This in turn blocks the ribosomes, the cell’s protein factory. Healthy cells detect blocked ribosomes and rapidly destroy useless proteins. If the necessary quality control machinery does not function properly, defective proteins accumulate and form toxic aggregates.