title: Characterization of the Neisseria Iga beta-core. The essential unit for outer membrane targeting and extracellular protein secretion.
abstract: Extracellular transport of Neisseria IgA proteases across the bacterial outer membrane is accomplished by the translocation function contained within the C-terminal Iga beta domain of IgA protease precursor proteins. Recently, we reported that Iga beta from N. gonorrhoeae MS11 (Val1097 to Phe1505), fused to a periplasmic passenger protein, facilitated its transport across the outer membrane, leading to surface exposure of the passenger. In the present work we show, by systematic N-terminal truncation of Iga beta, that the functional and structural unit, termed Iga beta-core, corresponds to the C-terminal approximately 274 amino acid residues (Ser1231 to Phe1505). This minimal region retains all the essential features necessary for the translocation of an N-terminally attached passenger across the outer membrane of Escherichia coli, and for its own correct integration into the outer membrane, even in the absence of a passenger protein. The membrane-integrated Iga beta-core constitutes a conserved entity found in the C-terminal regions of Iga beta domains of different N. gonorrhoeae, N. meningitidis and Haemophilus influenzae strains. In contrast, the surface-exposed N termini of the Iga beta domains vary in size and sequence. Based on secondary structure predictions, the key structural feature of the core is a beta-barrel (amphipathic, antiparallel transmembrane beta-strands, interspersed by hairpin turns and loops) which is common to many integral outer membrane proteins of Gram-negative bacteria. We propose that the core has been conserved in evolution, to provide a selective outer membrane export channel for covalently attached polypeptides.
authors.affiliation: Max-Planck-Institut für Biologie Abteilung Infektionsbiologie, Tübingen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Klauser
authors.forename: J
authors.initials: J
authors.lastname: Krämer
authors.forename: K
authors.initials: K
authors.lastname: Otzelberger
authors.forename: J
authors.initials: J
authors.lastname: Pohlner
authors.forename: T F
authors.initials: TF
authors.lastname: Meyer
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000032:analysis / Q000378:metabolism; D004926:Escherichia coli; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000201:enzymology* / Q000235:genetics; D009345:Neisseria meningitidis / Q000201:enzymology* / Q000235:genetics; D010447:Peptide Hydrolases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D010957:Plasmids; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D011498:Protein Precursors; D011994:Recombinant Proteins; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases; C021433:IgA-specific serine endopeptidase