title: An outer-membrane porin inducible by short-chain amides and urea in the methylotrophic bacterium Methylophilus methylotrophus.
abstract: The fmdA and fmdB genes encoding formamidase and a putative regulatory protein, respectively, from the methylotrophic bacterium Methylophilus methylotrophus were recloned with additional flanking DNA (pSW1). fmdC, encoding a weakly hydrophilic protein containing an N-terminal signal sequence, was identified upstream of fmdAB. The derived amino acid sequence of mature FmdC (M(r) 39204) showed that it was rich in beta-sheet and aromatic amino acids, and exhibited significant similarities to several outer-membrane porins from other bacteria. Cell fractionation studies showed that the protein was located in the outer membrane. Mature FmdC was purified and shown to consist of a single type of subunit (M(r) 40,000) with the predicted N-terminal amino acid sequence (GATISF-). SDS-PAGE and Western blotting of cells grown in continuous culture under various conditions showed that mature FmdC was induced by formamide, acetamide and urea, repressed by excess ammonia, and over-expressed during prolonged growth under formamide limitation. It is concluded that mature FmdC is a porin involved in the transport of short-chain amides and urea through the outer membrane of M. methylotrophus under conditions where these nitrogen sources are present at very low concentration.
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: James
authors.initials: J
authors.lastname: Mills
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Greenwood
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Wyborn
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Williams
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: Colin W
authors.initials: CW
authors.lastname: Jones
mesh_terms: D000577:Amides / Q000494:pharmacology*; D000581:Amidohydrolases / Q000235:genetics*; D000595:Amino Acid Sequence; D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D018272:Porins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D014508:Urea / Q000494:pharmacology*
chemical_list: D000577:Amides; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C107802:FmdC protein, Methylophilus methylotrophus; D018272:Porins; D014508:Urea; D000581:Amidohydrolases; C101846:formamidase