title: Characterization of porin from Roseobacter denitrificans.
abstract: Porin from Roseobacter denitrificans was isolated and purified to homogeneity. The pore characteristics from this marine bacterium were compared to those of its phylogenetically closely related freshwater bacteria Rhodobacter capsulatus, Rhodobacter sphaeroides and Rhodopseudomonas blastica. The porin formed weakly cation-selective, general diffusion pores in lipid bilayer membranes. High transmembrane potentials caused channel closing in steps that were of one or two thirds of the initial on-steps indicating that the porin of R. denitrificans comprised three more or less independent channels similar to PhoE and OmpC of Escherichia coli and the porin of Rhodobacter capsulatus. 37b4 Prediction of the secondary structure of the 36 N-terminal amino acid residues indicated two transmembrane beta-strands similar to those of the porins of Rhodobacter capsulatus 37b4 and Rhodopseudomonas blastica. Differences of the single channel conductivities between the porin of R. denitrificans and those of the related freshwater bacteria show that R. denitrificans evolved porin channels that are well adapted to the marine habitat.
authors.affiliation: Institut für Biologie II, Universität Freiburg, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Neumann
authors.forename: E
authors.initials: E
authors.lastname: Maier
authors.forename: E
authors.initials: E
authors.lastname: Schiltz
authors.forename: J
authors.initials: J
authors.lastname: Weckesser
authors.forename: R
authors.initials: R
authors.lastname: Benz
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D029968:Escherichia coli Proteins; D006088:Gram-Negative Aerobic Bacteria / Q000737:chemistry*; D007473:Ion Channels / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism; D008969:Molecular Sequence Data; D018272:Porins / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D017433:Protein Structure, Secondary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D018272:Porins; C082922:PhoE protein, E coli