The inclusion of an atypical amino acid in their proteins allows Salmonella bacteria to resist certain antibiotics.

Until now, scientists thought that organisms used only α-amino acids to build their proteins. But Michael Ibba at Ohio State University in Columbus and his team have found that Salmonella make the structurally different β version of the amino acid lysine. In the bacteria, an enzyme called PoxA binds to β-lysine and passes it to the protein EF-P, which functions as a transfer-RNA mimic during protein synthesis. The researchers show that EF-P, a protein essential to Salmonella's virulence, is active only when it contains β-lysine.

Ibba's team think that the β-lysine-incorporation pathway could represent a new target for effective antibiotics against Salmonella.

Nature Chem. Biol. 10.1038/NCHEMBIO.632 (2011)