title: Supramolecular organization of the repetitive backbone unit of the Streptococcus pneumoniae pilus.
abstract: Streptococcus pneumoniae, like many other Gram-positive bacteria, assembles long filamentous pili on their surface through which they adhere to host cells. Pneumococcal pili are formed by a backbone, consisting of the repetition of the major component RrgB, and two accessory proteins (RrgA and RrgC). Here we reconstruct by transmission electron microscopy and single particle image reconstruction method the three dimensional arrangement of two neighbouring RrgB molecules, which represent the minimal repetitive structural domain of the native pilus. The crystal structure of the D2-D4 domains of RrgB was solved at 1.6 A resolution. Rigid-body fitting of the X-ray coordinates into the electron density map enabled us to define the arrangement of the backbone subunits into the S. pneumoniae native pilus. The quantitative fitting provide evidence that the pneumococcal pilus consists uniquely of RrgB monomers assembled in a head-to-tail organization. The presence of short intra-subunit linker regions connecting neighbouring domains provides the molecular basis for the intrinsic pilus flexibility.
authors.affiliation: Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America. gspraggon@gnf.org
authors.forename: Glen
authors.initials: G
authors.lastname: Spraggon
authors.forename: Eric
authors.initials: E
authors.lastname: Koesema
authors.forename: Maria
authors.initials: M
authors.lastname: Scarselli
authors.forename: Enrico
authors.initials: E
authors.lastname: Malito
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Biagini
authors.forename: Nathalie
authors.initials: N
authors.lastname: Norais
authors.forename: Carla
authors.initials: C
authors.lastname: Emolo
authors.forename: Michèle Anne
authors.initials: MA
authors.lastname: Barocchi
authors.forename: Fabiola
authors.initials: F
authors.lastname: Giusti
authors.forename: Markus
authors.initials: M
authors.lastname: Hilleringmann
authors.forename: Rino
authors.initials: R
authors.lastname: Rappuoli
authors.forename: Scott
authors.initials: S
authors.lastname: Lesley
authors.forename: Antonello
authors.initials: A
authors.lastname: Covacci
authors.forename: Vega
authors.initials: V
authors.lastname: Masignani
authors.forename: Ilaria
authors.initials: I
authors.lastname: Ferlenghi
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D018360:Crystallography, X-Ray; D010861:Fimbriae, Bacterial; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013296:Streptococcus pneumoniae / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins