Structure of the month - July 2009
Proc. Natl. Acad. Sci. USA Vol. 106, 2009, Pages 9661-9666
IpaB-IpgC interaction defines binding motif for type III secretion translocator
Michele Lunelli*, Ravi Kumar Lokareddy*, Arturo Zychlinsky, and Michael Kolbe
Department of Cellular Microbiology, Max-Planck-Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
* These authors contributed equally to this work
The delivery of virulence factors into host cells through type III secretion systems is essential for enterobacterial pathogenesis. Molecular chaperones bind specifically to virulence factors in the bacterial cytosol before secretion. Invasion plasmid gene C (IpgC) is a chaperone that binds two essential virulence factors of Shigella: invasion plasmid antigens (Ipa) B and C. Here we report the first crystal structure of IpgC alone and in complex with the chaperone binding domain (CBD) of IpaB. The chaperone captures the CBD in an extended conformation which is stabilized by conserved residues lining the cleft. Analysis of the co-crystal structure reveals a sequence motif which is functional in the IpaB translocator class from different bacteria as determined by isothermal titration calorimetry (ITC). Our results show how translocators are chaperoned and may allow the design of inhibitors of enterobacterial diseases.
Proc Natl Acad Sci USA. 2009 Jun 16;106(24):9661-6.