InterPro: IPR006315 Outer membrane autotransporter barrel

The secretion of protein products occurs by a number of different pathways in bacteria and several secretion mechanisms have been described for Gram-negative bacteria [1], an increasing number employ a highly efficient but simple mechanism first described for the immunoglobulin A1 (IgA1) proteases [2, 3].

The autotransporter secretion pathway [4] is a distinct secretion mechanism, in which the protein moiety mediating export through the outer membrane is contained within the precursor of the secreted protein itself. Autotransporters have been implicated as important or putative virulence factors [4] such as mediating adhesion to host cells or by mediating actin-promoted bacterial mobility [5].

The key feature of an autotransporter is that it contains all the information for secretion in the precursor of the secreted protein itself [4]. Autotransporters comprise three functional domains: 1) an N-terminal targeting domain (amino-terminal leader sequence) that functions as a signal peptide to mediate targeting to and translocation across the inner membrane 2) a C-terminal translocation domain (carboxy-terminal) that forms a beta-barrel pore to allow the secretion [6] of 3) the passenger domain, the secreted mature protein [2].

This entry shows the C-terminal autotransporter domain, it is about 400 amino acids in length and includes the aromatic amino acid-rich OMP signal, typically ending with a Phe or Trp residue, at the extreme C terminus.