title: A gene encoding a membrane protein exists upstream of the amoA/amoB genes in ammonia oxidizing bacteria: a third member of the amo operon?
abstract: The gene cluster encoding ammonia monooxygenase (AMO) in the chemolithotrophic soil bacterium Nitrosospira sp. NpAV was found to contain a third open reading frame, termed amoC, upstream of the genes amoA and amoB that encode the subunits of AMO. The amoC gene and its flanking regions were isolated and sequenced from a 4.4 kb EcoRI fragment that contains one of three copies of the ammonia monooxygenase gene cluster. The presence of this gene upstream of the other two amoA gene copies in Nitrosospira NpAV as well as upstream of amoA genes in the genomes of other ammonia oxidizing nitrifiers (strains in the genera Nitrosomonas, Nitrosopira, Nitrosolobus and Nitrosovibrio) was confirmed using genomic DNA, oligodeoxyribonucleotide primers and the PCR. The amoC gene in Nitrosospira sp. NpAV encodes a 270 amino acid polypeptide of approximately 36 kDa. Topological analysis of the predicted primary structure revealed 6 membrane spanning domains. The amoC gene was expressed in recombinant Escherichia coli from its indigenous promoter.
authors.affiliation: Department of Biology, University of Colorado, Denver 80217-3364, USA. mgklotz@carbon.cudenver.edu
authors.forename: M G
authors.initials: MG
authors.lastname: Klotz
authors.forename: J
authors.initials: J
authors.lastname: Alzerreca
authors.forename: J M
authors.initials: JM
authors.lastname: Norton
mesh_terms: D000595:Amino Acid Sequence; D000641:Ammonia / Q000378:metabolism; D001483:Base Sequence; D041841:Bradyrhizobiaceae / Q000201:enzymology / Q000235:genetics*; D002462:Cell Membrane / Q000201:enzymology; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D018628:Gene Dosage; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames / Q000235:genetics; D009876:Operon / Q000235:genetics*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics*; D011993:Recombinant Fusion Proteins; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase