In situstructure of theLegionellaDot/Icm type IV secretion system by electron cryotomography.
Type IV secretion systems (T4SSs) are large macromolecular machines that translocate protein and DNA and are involved in the pathogenesis of multiple human diseases. Here, using electron cryotomography (ECT), we report thein situstructure of the Dot/Icm type IVB secretion system (T4BSS) utilized by the human pathogenLegionella pneumophilaThis is the first structure of a type IVB secretion system, and also the first structure of any T4SSin situWhile the Dot/Icm system shares almost no sequence similarity with type IVA secretion systems (T4ASSs), its overall structure is seen here to be remarkably similar to previously reported T4ASS structures (those encoded by the R388 plasmid inEscherichia coliand the cag pathogenicity island inHelicobacter pylori). This structural similarity suggests shared aspects of mechanism. However, compared to the negative-stain reconstruction of the purified T4ASS from the R388 plasmid, theL. pneumophilaDot/Icm system is approximately twice as long and wide and exhibits several additional large densities, reflecting type-specific elaborations and potentially better structural preservationin situ.
California Institute of Technology, Pasadena, CA, USA.
Debnath
D
Ghosal
California Institute of Technology, Pasadena, CA, USA.
Yi-Wei
YW
Chang
Washington University School of Medicine, St. Louis, MO, USA.
Kwangcheol C
KC
Jeong
Washington University School of Medicine, St. Louis, MO, USA.
Joseph P
JP
Vogel
California Institute of Technology, Pasadena, CA, USA jensen@caltech.edu.|Howard Hughes Medical Institute, Pasadena, CA, USA.
Grant J
0000-0003-1556-4864
GJ
Jensen
D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure; D055032:Electron Microscope Tomography / Q000379:methods*; D015964:Gene Expression Regulation, Bacterial; D016952:Legionella pneumophila / Q000737:chemistry* / Q000235:genetics / Q000472:pathogenicity / Q000648:ultrastructure; D010957:Plasmids; D000069319:Type IV Secretion Systems / Q000737:chemistry* / Q000648:ultrastructure*
D001426:Bacterial Proteins; D000069319:Type IV Secretion Systems

Legionella pneumophila
; Dot/Icm; Type IV secretion systems; electron cryotomography; subtomogram averaging