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The Respiratory Terminal Oxidases of Cyanobacteria

The Respiratory Terminal Oxidases of Cyanobacteria. ALL CYANOBACTERIA CONTAIN AN AEROBIC RESPIRATORY CHAIN. Key enzymes of respiration : Respiratory Terminal Oxidases (RTOs). O 2 + 4 e - + 4 H +  2 H 2 O. Cyanobacterial RTOs: 3 protein families. 1) Heme-Cu oxidases and relatives.

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The Respiratory Terminal Oxidases of Cyanobacteria

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  1. The Respiratory Terminal Oxidases of Cyanobacteria

  2. ALL CYANOBACTERIA CONTAIN AN AEROBIC RESPIRATORY CHAIN

  3. Key enzymes of respiration: Respiratory Terminal Oxidases (RTOs) O2 + 4 e- + 4 H+ 2 H2O

  4. Cyanobacterial RTOs: 3 protein families • 1) Heme-Cu oxidases and relatives 2) Quinol oxidases (Qox), homologues of cytochrome bd from E. coli 3) Cyanide-insensitive quinol oxidases, homologues of plastid oxidase Ptox

  5. At least five different enzymes of group 1 exist in cyanobacteria:  a) Mitochondrial-type cytochrome c oxidases. Electron donor: cytochrome c. invariably 3 subunits with genes always arranged in the order coxBAC encoding subunits II, I, and III, respectively (Cox) b) Cytochrome cbb3 . Rare in cyanobacteria. In Synechococcus sp. PCC7942 the enzyme is a genuine cytochrome c oxidase despite having only 2 of the 8 subunits known from purple bacteria c) Three different types of ARTO (Alternate Respiratory Terminal Oxidases)

  6. Definition of ARTO: • Three subunits with marked sequence similarity to the corresponding three subunits of cyanobacterial cytochrome c oxidase. • 2)In most cases (but not always: an exception exists in Synechocystis sp. strain PCC6803) the gene arrangement is BAC, as with genuine cytochrome c oxidases • 3)At least one of the two following marker-sequences of genuine cytochrome c oxidase is NOT present:

  7. Subunit I: Mg2+ binding site essential for transmembrane translocation of H+ Cytochrome c oxidase (Cox) WAHHMF ARTO (mostly, but not universally) WVHHMF Subunit II: Cu2+ binding site essential for transfer of electrons from cytochrome c Cytochrome c oxidase (Cox) CaElCgpyHgvM ARTO DsqfSGaYfatm

  8. ARTO type1: Subunit I: ARTO sequence Subunit II: ARTO sequence ARTO type2: Subunit I: ARTO sequence Subunit II: Cox sequence ARTO type3: Subunit I: Cox sequence Subunit II: ARTO sequence Electron donors for ARTO are not known

  9. STRAIN Cox cbb3 ARTOtype1 ARTOtype2 ARTOtype3 Qox Ptox Nostoc (Anabaena) sp. PCC7120 1 0 1 1 0 1 1 Anabaena variabilis ATCC29413 1 0 3 1 0 4 1 Nostoc punctiforme PCC73102 1 0 2 1 0 0 1 Trichodesmium erythraeum IMS101 0 0 1 1 0 0 0 Synechococcus sp. PCC6301 1 1 0 0 0 1 0 Synechococcus sp. PCC7942 1 1 0 0 0 1 0 Synechococcus sp. CC9605 1 0 1 0 0 0 0 Synechococcus sp. CC9902 1 0 0 0 0 0 1 Synechococcus sp. CC9311 1 0 0 0 1 0 0 Synechococcus sp.JA-3-3Ab 1 0 0 0 0 1 0 Synechococcus sp.JA-2-3B’a(2-13) 1 0 0 0 0 1 0 Synechococcus sp. WH8102 1 0 0 0 1 0 1 Synechococcus sp. RCC307 1 0 1 0 0 0 1 Synechococcus sp. PCC7002 1 0 1 0 0 0 1 Synechocystis sp. PCC6803 1 0 1 0 0 1 0 Thermosynechococcus elongatus BP-1 0 1 0 1 0 1 0 Microcystis aeruginosa NIES-843 1 0 0 0 0 0 0 Crocosphaera watsonii WH8501 1 0 1 0 0 0 0 Cyanothece sp. PCC7424 1 0 1 0 0 1(?) 0 Cyanothece sp. PCC8801 1 0 0 0 0 0 0 Cyanothece sp. ATCC51142 1 0 2 0 0 1 0 Acaryochloris marina MBIC 11017 1 0 0 0 0 1 3 Gloeobacter violaceus PCC7421 1 0 0 0 0 1 1 Prochlorococcus marinus SS120 1 0 0 0 0 0 0 Prochlorococcus marinus MED4 1 0 0 0 0 0 1 Prochlorococcus marinus MIT9301 1 0 0 0 0 0 1 Prochlorococcus marinus MIT9303 1 0 0 0 0 0 0 Prochlorococcus marinus MIT9312 1 0 0 0 0 0 1 Prochlorococcus marinus MIT9313 1 0 0 0 0 0 0 Prochlorococcus marinus MIT9515 1 0 1 0 0 0 0 Prochlorococcus marinus NATL1A 1 0 0 0 0 0 1 Prochlorococcus marinus NATL2A 1 0 0 0 0 0 1 Prochlorococcus marinus AS9601 1 0 0 0 0 0 1

  10. 1. All cyanobacteria contain at least 1 RTO 2. No RTO is present in all cyanobacteria 3. The set of RTOs present in a cyanbacterium varies widely from strain to strain, even among closely related strains

  11. Postulate In every cyanobacterium that contains more than 1 RTO, each RTO must have a specific function

  12. Example Synechocystis sp. PCC6803 ________________________________________________________________________________________________________________________________ 1. Cox: essential for heterotrophic growth 2. ARTO: energization of the CM 3. Quinol oxidase (bd-type): valve for dissipation of surplus electrons in Q-pool

  13. Bioenergetic pathways in Synechocystis 6803 DBMIB DBMIB

  14. Bioenergetic electron transport is a complex regulon with one set of substances, the quinone pool being the sole common component of all pathways

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