Supramolecular organization of the repetitive backbone unit of the Streptococcus pneumoniae pilus.
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.
Spraggon
Glen
G
Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America. gspraggon@gnf.org
Koesema
Eric
E
Scarselli
Maria
M
Malito
Enrico
E
Biagini
Massimiliano
M
Norais
Nathalie
N
Emolo
Carla
C
Barocchi
Michèle Anne
MA
Giusti
Fabiola
F
Hilleringmann
Markus
M
Rappuoli
Rino
R
Lesley
Scott
S
Covacci
Antonello
A
Masignani
Vega
V
Ferlenghi
Ilaria
I
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*
D001426:Bacterial Proteins