2. The Respiratory Terminal Oxidases of Cyanobacteria

3. ALL CYANOBACTERIA CONTAIN AN AEROBIC RESPIRATORY CHAIN

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

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

6. 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 cbb 3. 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)

7. Definition of ARTO: 1)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:

8. Subunit I: Mg 2+ binding site essential for transmembrane translocation of H+ Cytochrome c oxidase (Cox) WAHHMF ARTO (mostly, but not universally) WVHHMF Subunit II: Cu 2+ binding site essential for transfer of electrons from cytochrome c Cytochrome c oxidase(Cox) CaElCgpyHgvM ARTO DsqfSGaYfatm

9. 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

10. 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

11. 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

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

13. 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

14. Bioenergetic pathways in Synechocystis 6803 DBMIB

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