Export of autotransported proteins proceeds through an oligomeric ring shaped by C-terminal domains.
An investigation was made into the oligomerization, the ability to form pores and the secretion-related properties of the 45 kDa C-terminal domain of the IgA protease (C-IgAP) from Neisseria gonorrhoeae. This protease is the best studied example of the autotransporters (ATs), a large family of exoproteins from Gram-negative bacteria that includes numerous virulence factors from human pathogens. These proteins contain an N-terminal passenger domain that em bodies the secreted polypeptide, while the C-domain inserts into the outer membrane (OM) and trans locates the linked N-module into the extracellular medium. Here we report that purified C-IgAP forms an oligomeric complex of approximately 500 kDa with a ring-like structure containing a central cavity of approximately 2 nm diameter that is the conduit for the export of the N-domains. These data overcome the previous model for ATs, which postulated the passage of the N-module through the hydrophilic channel of the beta-barrel of each monomeric C-domain. Our results advocate a secretion mechanism not unlike other bacterial export systems, such as the secretins or fimbrial ushers, which rely on multimeric complexes assembled in the OM.
Veiga
Esteban
E
Departmento de Biotecnología Microbiana, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, Madrid 28049, Spain.
Sugawara
Etsuko
E
Nikaido
Hiroshi
H
de Lorenzo
Víctor
V
Fernández
Luis Angel
LA
D001426:Bacterial Proteins / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism; D009344:Neisseria gonorrhoeae / Q000378:metabolism*; D018272:Porins / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport; D012697:Serine Endopeptidases / Q000378:metabolism* / Q000648:ultrastructure
D001426:Bacterial Proteins; D007473:Ion Channels; D018272:Porins; D012697:Serine Endopeptidases; C021433:IgA-specific serine endopeptidase