Crouching dragon guards nascent proteins

Cells contain a wide variety of chaperones to help newly synthesized proteins fold properly and reach their native state. But just how the chaperones operate isn't always clear. Now, Lars Ferbitz, Nenad Ban (Swiss Federal Institute of Technology, Zurich, Switzerland), Elke Deuerling (University of Heidelberg, Germany), and colleagues find that the trigger factor chaperone complexes with the ribosome and provides a protected cradle for newly forming proteins.

Ferbitz et al. resolved a 2.7 Å crystal structure of the E. coli trigger protein and of the NH₂-terminal domain of the trigger factor bound to the 50S ribosomal subunit of H. marismortui. The tail domain of the trigger factor binds to the ribosome with moderate affinity. The remainder of the protein—the head, back, and arms—loom over the tunnel where polypeptides exit the ribosome, appearing like...