Pertactin Processing and Secretion in Protease(s) Deficient Strains of Escherichia Coli Suggestive of the Possible Role of Proteases in Folding of Autotransporter Proteins

Many of the virulence determinants secreted from pathogenic Gram-negative bacteria are autotransporter proteins, which are usually either exported to the bacterial cell surface or secreted into the external environment. There appears to be dearth of information regarding the exact mechanism of their processing into the surface-exposed passenger domains and C-terminal, βdomains. The C-terminal porin domains mediate the final step of autotransporter secretion by threading of the passenger domain through the outer membrane (OM). The native structure is formed only after this final secretion step, which does not require any energy involvement. Despite sequence divergence and functional diversity among autotransporter passenger domains almost all of them are predicted to form parallel ß-helices, indicating this structural topology may be important for secretion. The possible involvement of periplasmic environment in regulating the export of pertactin, an autotransporter passenger domain from Bordetella pertussis is reported.