Evolution of the acceptor side of photosystem I: ferredoxin, flavodoxin, and ferredoxin-NADP+oxidoreductase.
The development of oxygenic photosynthesis by primordial cyanobacteria ~2.7 billion years ago led to major changes in the components and organization of photosynthetic electron transport to cope with the challenges of an oxygen-enriched atmosphere. We review herein, following the seminal contributions as reported by Jaganathan et al. (Functional genomics and evolution of photosynthetic systems, vol 33, advances in photosynthesis and respiration, Springer, Dordrecht, 2012), how these changes affected carriers and enzymes at the acceptor side of photosystem I (PSI): the electron shuttle ferredoxin (Fd), its isofunctional counterpart flavodoxin (Fld), their redox partner ferredoxin-NADP+reductase (FNR), and the primary PSI acceptors Fxand FA/FB. Protection of the [4Fe-4S] centers of these proteins from oxidative damage was achieved by strengthening binding between the FA/FBpolypeptide and the reaction center core containing Fx, therefore impairing O2access to the clusters. Immobilization of FA/FBin the PSI complex led in turn to the recruitment of new soluble electron shuttles. This function was fulfilled by oxygen-insensitive [2Fe-2S] Fd, in which the reactive sulfide atoms of the cluster are shielded from solvent by the polypeptide backbone, and in some algae and cyanobacteria by Fld, which employs a flavin as prosthetic group and is tolerant to oxidants and iron limitation. Tight membrane binding of FNR allowed solid-state electron transfer from PSI bridged by Fd/Fld. Fine tuning of FNR catalytic mechanism led to formidable increases in turnover rates compared with FNRs acting in heterotrophic pathways, favoring Fd/Fld reduction instead of oxygen reduction.
Instituto de Biología Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Ocampo y Esmeralda, 2000, Rosario, Argentina.
Juan José
JJ
Pierella Karlusich
Instituto de Biología Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Ocampo y Esmeralda, 2000, Rosario, Argentina. carrillo@ibr-conicet.gov.ar.
Néstor
N
Carrillo
D019143:Evolution, Molecular; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism*; D005288:Ferredoxins / Q000378:metabolism*; D005418:Flavodoxin / Q000378:metabolism*; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D052817:Phototrophic Processes
D005288:Ferredoxins; D005418:Flavodoxin; D045331:Photosystem I Protein Complex; D005287:Ferredoxin-NADP Reductase
Evolution; Ferredoxin; Ferredoxin-NADP+ reductase; Flavodoxin; Oxygenic photosynthesis; Photosystem I