title: Helical structure of the needle of the type III secretion system of Shigella flexneri.
abstract: Gram-negative bacteria commonly interact with animal and plant hosts using type III secretion systems (TTSSs) for translocation of proteins into eukaryotic cells during infection. 10 of the 25 TTSS-encoding genes are homologous to components of the bacterial flagellar basal body, which the TTSS needle complex morphologically resembles. This indicates a common ancestry, although no TTSS sequence homologues for the genes encoding the flagellum are found. We here present an approximately 16-A structure of the central component, the needle, of the TTSS. Although the needle subunit is significantly smaller and shares no sequence homology with the flagellar hook and filament, it shares a common helical architecture ( approximately 5.6 subunits/turn, 24-A helical pitch). This common architecture implies that there will be further mechanistic analogies in the functioning of these two bacterial systems.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
authors.forename: Frank S
authors.initials: FS
authors.lastname: Cordes
authors.forename: Kaoru
authors.initials: K
authors.lastname: Komoriya
authors.forename: Eric
authors.initials: E
authors.lastname: Larquet
authors.forename: Shixin
authors.initials: S
authors.lastname: Yang
authors.forename: Edward H
authors.initials: EH
authors.lastname: Egelman
authors.forename: Ariel
authors.initials: A
authors.lastname: Blocker
authors.forename: Susan M
authors.initials: SM
authors.lastname: Lea
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure; D005407:Flagella / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D007091:Image Processing, Computer-Assisted; D011487:Protein Conformation; D021381:Protein Transport; D012763:Shigella flexneri / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins