Characterization of the Ruler Protein Interaction Interface on the Substrate Specificity Switch Protein in the Type III Secretion System.

Many pathogenic Gram-negative bacteria use the type III secretion system (T3SS) to deliver effector proteins into eukaryotic host cells. In , the switch to secretion of effector proteins is induced first after intimate contact between the bacterium and its eukaryotic target cell has been established, and the T3SS proteins YscP and YscU play a central role in this process. Here we identify the molecular details of the YscP binding site on YscU by means of nuclear magnetic resonance (NMR) spectroscopy.