December 11, 2014

Bacterial secretion machinery: 3-D view

New structural findings reveal how “gatekeeper” proteins participate in the secretion systems bacteria use to infect host cells.

Many pathogenic bacteria use Type Three Secretion Systems (T3SS) to deliver bacterial proteins into host cells. These protein delivery machines are assembled in an ordered process, with translocator proteins that form the pore in the host cell being secreted before bacterial effector proteins. Conserved “gatekeeper” proteins are important to the ordered secretion of translocator proteins, but how gatekeepers regulate the process is unknown.

Tara Archuleta, Ph.D., and Benjamin Spiller, Ph.D., have determined the 3-D structure of a Chlamydial gatekeeper protein, in complex with a translocator-specific chaperone (a protein that binds to and protects translocator proteins). Their studies, reported Nov. 6 in PLOS Pathogens, identify a previously unknown interface between gatekeepers and translocator chaperones.

Disruption of the gatekeeper-chaperone interaction in Shigella disrupted secretion of translocators, demonstrating that this complex is a critical component of T3SS and is essential for the ordered secretion process. Understanding bacterial secretion systems could aid the development of novel antibiotics that block these protein delivery machines.

This research was supported by grants from the National Institutes of Health (AI072453, AI108778) and by Vanderbilt University.

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