Organization and coordinated assembly of the type III secretion export apparatus.
Type III protein secretion systems are unique bacterial nanomachines with the capacity to deliver bacterial effector proteins into eukaryotic cells. These systems are critical to the biology of many pathogenic or symbiotic bacteria for insects, plants, animals, and humans. Essential components of these systems are multiprotein envelope-associated organelles known as the needle complex and a group of membrane proteins that compose the so-called export apparatus. Here, we show that components of the export apparatus associate intimately with the needle complex, forming a structure that can be visualized by cryo-electron microscopy. We also show that formation of the needle complex base is initiated at the export apparatus and that, in the absence of export apparatus components, there is a significant reduction in the levels of needle complex base assembly. Our results show a substantial coordination in the assembly of the two central elements of type III secretion machines.
Wagner
Samuel
S
Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA.
Königsmaier
Lisa
L
Lara-Tejero
María
M
Lefebre
Matthew
M
Marlovits
Thomas C
TC
Galán
Jorge E
JE
D001426:Bacterial Proteins / Q000378:metabolism*; D015153:Blotting, Western; D020285:Cryoelectron Microscopy; D007091:Image Processing, Computer-Assisted; D047468:Immunoprecipitation; D026901:Membrane Transport Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism* / Q000648:ultrastructure; D012486:Salmonella typhimurium / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D055571:Secretory Pathway / Q000502:physiology*
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D046912:Multiprotein Complexes; C079790:PrgH protein, Salmonella typhimurium; C090991:invG protein, Salmonella typhimurium