title: The agglutination protein AggA from Shewanella oneidensis MR-1 is a TolC-like protein and forms active channels in vitro.
abstract: Type I secretion systems (TISS) are associated with the virulence of Gram-negative bacteria and the secretion of pathogenic molecular determinants. The Shewanella oneidensis MR-1 outer-membrane protein AggA is part of a TISS. Recombinant AggA expressed in Escherichia coli as inclusion bodies can be efficiently refolded in vitro, and can form active channel-tunnels as shown by proteoliposome swelling assays and electrophysiological measurements in lipid bilayers. Structure-based sequence alignments identify AggA as a TolC-like protein, and point to a conserved structural framework among such proteins despite their marginal sequence similarity. Phylogenetic analysis reveals that clustering of TolC-like proteins can be correlated with their involvement in TISS, Resistance/Nodulation/Division (RND) or Major Facilitator Superfamily (MFS) complexes. Taken together, our results establish a first set of structure-function relationships for a bacterial outer-membrane protein likely to be exclusively involved in TISS, and may contribute towards a more accurate classification of Outer-Membrane Factor (OMF) family proteins.
authors.affiliation: Laboratory for Protein Biochemistry and Biomolecular Engineering (L-ProBE), Ghent University, 9000 Ghent, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Theunissen
authors.forename: Bjorn
authors.initials: B
authors.lastname: Vergauwen
authors.forename: Lina
authors.initials: L
authors.lastname: De Smet
authors.forename: Jozef
authors.initials: J
authors.lastname: Van Beeumen
authors.forename: Patrick
authors.initials: P
authors.lastname: Van Gelder
authors.forename: Savvas N
authors.initials: SN
authors.lastname: Savvides
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000648:ultrastructure*; D004926:Escherichia coli / Q000378:metabolism; D008969:Molecular Sequence Data; D016062:Porosity; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000648:ultrastructure; D016415:Sequence Alignment; D020592:Shewanella / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D011994:Recombinant Proteins