Heme-copper oxidases and their electron donors in cyanobacterial respiratory electron transport.
Cyanobacteria are the paradigmatic organisms of oxygenic (plant-type) photosynthesis and aerobic respiration. Since there is still an amazing lack of knowledge on the role and mechanism of their respiratory electron transport, we have critically analyzed all fully or partially sequenced genomes for heme-copper oxidases and their (putative) electron donors cytochrome c(6), plastocyanin, and cytochrome c(M). Well-known structure-function relationships of the two branches of heme-copper oxidases, namely cytochrome c (aa(3)-type) oxidase (COX) and quinol (bo-type) oxidase (QOX), formed the base for a critical inspection of genes and ORFs found in cyanobacterial genomes. It is demonstrated that at least one operon encoding subunits I-III of COX is found in all cyanobacteria, whereas many non-N(2)-fixing species lack QOX. Sequence analysis suggests that both cyanobacterial terminal oxidases should be capable of both the four-electron reduction of dioxygen and proton pumping. All diazotrophic organisms have at least one operon that encodes QOX. In addition, the highly refined specialization in heterocyst forming Nostocales is reflected by the presence of two paralogs encoding COX. The majority of cyanobacterial genomes contain one gene or ORF for plastocyanin and cytochrome c(M), whereas 1-4 paralogs for cytochrome c(6) were found. These findings are discussed with respect to published data about the role of respiration in wild-type and mutated cyanobacterial strains in normal metabolism, stress adaptation, and nitrogen fixation. A model of the branched electron-transport pathways downstream of plastoquinol in cyanobacteria is presented.
Bernroitner
Margit
M
Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, (phone: +43-1-36006-6073; fax: +43-1-36006-6059).
Zamocky
Marcel
M
Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, (phone: +43-1-36006-6073; fax: +43-1-36006-6059).|Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, SK-84551 Bratislava.
Pairer
Martin
M
Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, (phone: +43-1-36006-6073; fax: +43-1-36006-6059).
Furtmüller
Paul G
PG
Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, (phone: +43-1-36006-6073; fax: +43-1-36006-6059).
Peschek
Günter A
GA
Department of Physical Chemistry, Molecular Bioenergetics Group, University of Vienna, Althanstraße 14, A-1090 Vienna.
Obinger
Christian
C
Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, (phone: +43-1-36006-6073; fax: +43-1-36006-6059).
D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis
D010088:Oxidoreductases; C020094:duroquinol oxidase; D003576:Electron Transport Complex IV