title: Topology of the Erwinia chrysanthemi oligogalacturonate porin KdgM.
abstract: The Erwinia chrysanthemi oligogalacturonate-specific monomeric porin, KdgM, does not present homology with any porins of known structure. A model of this protein, based on sequence similarity and the amphipathy profile, was constructed. The model depicts a beta-barrel composed of 14 antiparallel beta-strands. The accuracy of this model was tested by the chemical labelling of cysteine residues introduced by site-directed mutagenesis. The protein has seven surface-exposed loops. They are rather small with the exception of one, loop L6. Deletion of this loop allowed the entry of maltopentaose into the bacteria, a molecule too large to enter through the wild-type KdgM. Loop L6 could fold back into the lumen of the pore and play the role of the constriction loop L3 of general porins. With 14 transmembrane segments, the KdgM porin family could represent the smallest porin characterized to date.
authors.affiliation: Unité Microbiologie et Génétique, UMR CNRS-INSA-UCB 5122, Batiment Lwoff, 10 rue Raphaël Dubois, 69622 Villeurbanne, France.
authors.forename: Teijo
authors.initials: T
authors.lastname: Pellinen
authors.forename: Helena
authors.initials: H
authors.lastname: Ahlfors
authors.forename: Nicolas
authors.initials: N
authors.lastname: Blot
authors.forename: Guy
authors.initials: G
authors.lastname: Condemine
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D017931:DNA Primers / Q000737:chemistry; D016974:Dickeya chrysanthemi / Q000737:chemistry*; D024881:Drug Resistance, Bacterial; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000737:chemistry; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009844:Oligosaccharides / Q000378:metabolism / Q000494:pharmacology*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D018272:Porins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011487:Protein Conformation; D017510:Protein Folding; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D009844:Oligosaccharides; D018272:Porins; C412763:oligogalacturonic acid; C019193:maltopentaose; D003545:Cysteine