title: Respiratory terminal oxidases in the facultative chemoheterotrophic and dinitrogen fixing cyanobacterium Anabaena variabilis strain ATCC 29413: characterization of the cox2 locus.
abstract: Upon nitrogen step-down, some filamentous cyanobacteria differentiate heterocysts, cells specialized for dinitrogen fixation, a highly oxygen sensitive process. Aerobic respiration is one of the mechanisms responsible for a microaerobic environment in heterocysts and respiratory terminal oxidases are the key enzymes of the respiratory chains. We used Anabaena variabilis strain ATCC 29413, because it is one of the few heterocyst-forming facultatively chemoheterotrophic cyanobacteria amenable to genetic manipulation. Using PCR with degenerate primers, we found four gene loci for respiratory terminal oxidases, three of which code for putative cytochrome c oxidases and one whose genes are homologous to cytochrome bd-type quinol oxidases. One cytochrome c oxidase, Cox2, was the only enzyme whose expression, tested by RT-PCR, was evidently up-regulated in diazotrophy, and therefore cloned, sequenced, and characterized. Up-regulation of Cox2 was corroborated by Northern and primer extension analyses. Strains were constructed lacking Cox1 (a previously characterized cytochrome c oxidase), Cox2, or both, which all grew diazotrophically. In vitro cytochrome c oxidase and respiratory activities were determined in all strains, allowing for the first time to estimate the relative contributions to total respiration of the different respiratory electron transport branches under different external conditions. Especially adding fructose to the growth medium led to a dramatic enhancement of in vitro cytochrome c oxidation and in vivo respiratory activity without significantly influencing gene expression.
authors.affiliation: Institut für Physikalische Chemie, Universität Wien, UZA2, Althanstrasse 14, A-1090 Vienna, Austria. dietmar.pils@univie.ac.at
authors.forename: Dietmar
authors.initials: D
authors.lastname: Pils
authors.forename: Corinna
authors.initials: C
authors.lastname: Wilken
authors.forename: Ana
authors.initials: A
authors.lastname: Valladares
authors.forename: Enrique
authors.initials: E
authors.lastname: Flores
authors.forename: Georg
authors.initials: G
authors.lastname: Schmetterer
mesh_terms: D000595:Amino Acid Sequence; D046870:Anabaena variabilis / Q000201:enzymology* / Q000235:genetics*; D019069:Cell Respiration / Q000502:physiology*; D051546:Cyclooxygenase 2; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009584:Nitrogen / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D007527:Isoenzymes; D011994:Recombinant Proteins; D010088:Oxidoreductases; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D009584:Nitrogen