A polymorphic helix of a Salmonella needle protein relays signals defining distinct steps in type III secretion
by Emily Z. Guo, Daniel C. Desrosiers, Jan Zalesak, James Tolchard, M élanie Berbon, Birgit Habenstein, Thomas Marlovits, Antoine Loquet, Jorge E. Galán
Type III protein-secretion machines are essential for the interactions of many pathogenic or symbiotic bacterial species with their respective eukaryotic hosts. The core component of these machines is the injectisome, a multiprotein complex that mediates the selection of substrates, their passage through the bacterial envelope, and ultimately their delivery into eukaryotic target cells. The injectisome is composed of a large cytoplasmic complex or sorting platform, a multiring base embedded in the bacterial envelope, and a needle-like filament that protrudes several nanometers from the bacte rial surface and is capped at its distal end by the tip complex. A characteristic feature of these machines is that their activity is stimulated by contact with target host cells. The sensing of target cells, thought to be mediated by the distal tip of the needle filament, generates an activating si gnal that must be transduced to the secretion machine by the needle filament. Here, through a multidisciplinary approach, including solid-state NMR (SSNMR) and cryo electron microscopy (cryo-EM) analyses, we have identified critical residues of the needle filament protein of aSalmonella Typhimurium type III secretion system that are involved in the regulation of the activity of the secretion machine. We found that mutations in the needle fi...
Source: PLoS Biology: Archived Table of Contents - Category: Biology Authors: Emily Z. Guo Source Type: research