title: Structure of a type IV secretion system core complex.
abstract: Type IV secretion systems (T4SSs) are important virulence factors used by Gram-negative bacterial pathogens to inject effectors into host cells or to spread plasmids harboring antibiotic resistance genes. We report the 15 angstrom resolution cryo-electron microscopy structure of the core complex of a T4SS. The core complex is composed of three proteins, each present in 14 copies and forming a approximately 1.1-megadalton two-chambered, double membrane-spanning channel. The structure is double-walled, with each component apparently spanning a large part of the channel. The complex is open on the cytoplasmic side and constricted on the extracellular side. Overall, the T4SS core complex structure is different in both architecture and composition from the other known double membrane-spanning secretion system that has been structurally characterized.
authors.affiliation: Institute of Structural and Molecular Biology, School of Crystallography, Birkbeck College, Malet Street, London, WC1E 7HX, UK.
authors.forename: Rémi
authors.initials: R
authors.lastname: Fronzes
authors.forename: Eva
authors.initials: E
authors.lastname: Schäfer
authors.forename: Luchun
authors.initials: L
authors.lastname: Wang
authors.forename: Helen R
authors.initials: HR
authors.lastname: Saibil
authors.forename: Elena V
authors.initials: EV
authors.lastname: Orlova
authors.forename: Gabriel
authors.initials: G
authors.lastname: Waksman
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*; D003001:Cloning, Molecular; D020285:Cryoelectron Microscopy; D006090:Gram-Negative Bacteria / Q000737:chemistry* / Q000235:genetics / Q000472:pathogenicity; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000648:ultrastructure; D010957:Plasmids; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D037521:Virulence Factors / Q000737:chemistry* / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D046912:Multiprotein Complexes; D037521:Virulence Factors