title: 3D structure of EspA filaments from enteropathogenic Escherichia coli.
abstract: The type III secretion system (TTSS) is a modular apparatus assembled by many pathogenic Gram-negative bacteria and is designed to translocate proteins through the bacterial cell wall into the eukaryotic host cell. The conserved components of the TTSS comprise stacks of rings spanning the inner and outer bacterial membrane and a narrow, needle-like structure projecting outwards. The TTSS of enteropathogenic E. coli is unique in that one of the translocator proteins, EspA, polymerizes to form an extension to the needle complex which interacts with the host cell. In this study we present the 3D structure of EspA filaments to c. 26 A resolution determined from electron micrographs of negatively stained preparations by image processing. The structure comprises a helical tube with a diameter of 120 A enclosing a central channel of 25 A diameter through which effector proteins may be transported. The subunit arrangement corresponds to a one-start helix with 28 subunits present in five turns of the helix and an axial rise of 4.6 A per subunit. This is the first report of a 3D structure of a filamentous extension to the TTSS.
authors.affiliation: Centre for Molecular Microbiology and Infection, Department of Biological Sciences, Imperial College, London, SW7 2AZ, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Daniell
authors.forename: Eva
authors.initials: E
authors.lastname: Kocsis
authors.forename: Edward
authors.initials: E
authors.lastname: Morris
authors.forename: Stuart
authors.initials: S
authors.lastname: Knutton
authors.forename: Frank P
authors.initials: FP
authors.lastname: Booy
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
mesh_terms: D000818:Animals; D004926:Escherichia coli / Q000737:chemistry* / Q000378:metabolism* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D005407:Flagella / Q000737:chemistry; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; C102051:EspA protein, E coli; D021122:Protein Subunits