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- Title
Structure of the outer membrane complex of a type IV secretion system.
- Authors
Chandran, Vidya; Fronzes, Rémi; Duquerroy, Stéphane; Cronin, Nora; Navaza, Jorge; Waksman, Gabriel
- Abstract
Type IV secretion systems are secretion nanomachines spanning the two membranes of Gram-negative bacteria. Three proteins, VirB7, VirB9 and VirB10, assemble into a 1.05 megadalton (MDa) core spanning the inner and outer membranes. This core consists of 14 copies of each of the proteins and forms two layers, the I and O layers, inserting in the inner and outer membrane, respectively. Here we present the crystal structure of a ∼0.6 MDa outer-membrane complex containing the entire O layer. This structure is the largest determined for an outer-membrane channel and is unprecedented in being composed of three proteins. Unexpectedly, this structure identifies VirB10 as the outer-membrane channel with a unique hydrophobic double-helical transmembrane region. This structure establishes VirB10 as the only known protein crossing both membranes of Gram-negative bacteria. Comparison of the cryo-electron microscopy (cryo-EM) and crystallographic structures points to conformational changes regulating channel opening and closing.
- Subjects
GRAM-negative bacteria; PROTEINS; BIOLOGICAL membranes; HYDROPHOBIC surfaces; CRYSTALLOGRAPHY; SECRETION; ULTRASTRUCTURE (Biology); ELECTRON microscopy; OPTICS
- Publication
Nature, 2009, Vol 462, Issue 7276, p1011
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature08588