title: Molecular and functional characterisation of the Serratia marcescens outer membrane protein Omp1.
abstract: Serratia marcescens outer membrane contains three different general diffusion porins: Omp1, Omp2 and Omp3. Omp1 was cloned and sequenced and it shows a great homology to the family of outer membrane porins that comprises the general porins of enteric bacteria. The gene for Omp1 was transferred into an expression plasmid and was expressed in Escherichia coli UH302 (E. coli UH302 pOM100), a porin deficient strain. Its expression confers a higher susceptibility towards different antibiotics to this strain. Omp1 was purified to homogeneity from outer membrane of E. coli UH302 pOM100. Reconstitution of the purified protein into black lipid bilayers demonstrated that it is a channel-forming component with a single-channel conductance of approximately 2 nS in 1 M KCl similar to that of other porins from enteric bacteria. Omp1 is slightly cation-selective. Its homology to already crystallised members of the family of enteric porins whose three-dimensional-structures are known and allowed the design of a topology model for Omp1. The charge distribution within a porin monomer is similar as in other general diffusion pores. The positively charged amino acids localised at the beta-strands opposite the external loop L3, which restrict the pore diameter in the porin monomer.
authors.affiliation: Laboratory of Microbiology. Biomedical Research Centre of Bellvitge, University of Barcelona, E-08907 L'Hospitalet, Barcelona, Spain.
authors.forename: Neus
authors.initials: N
authors.lastname: Ruiz
authors.forename: Elke
authors.initials: E
authors.lastname: Maier
authors.forename: Christian
authors.initials: C
authors.lastname: Andersen
authors.forename: Roland
authors.initials: R
authors.lastname: Benz
authors.forename: Miguel
authors.initials: M
authors.lastname: Viñas
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D003001:Cloning, Molecular; D004553:Electric Conductivity; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D008564:Membrane Potentials / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018272:Porins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012706:Serratia marcescens / Q000235:genetics*; D040681:Structural Homology, Protein
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D018272:Porins; D011994:Recombinant Proteins