Mobile hydrogen carbonate acts as proton acceptor in photosynthetic water oxidation.
Cyanobacteria, algae, and plants oxidize water to the O2 we breathe, and consume CO2 during the synthesis of biomass. Although these vital processes are functionally and structurally well separated in photosynthetic organisms, there is a long-debated role for CO2/ in water oxidation. Using membrane-inlet mass spectrometry we demonstrate that acts as a mobile proton acceptor that helps to transport the protons produced inside of photosystem II by water oxidation out into the chloroplast's lumen, resulting in a light-driven production of O2 and CO2. Depletion of from the media leads, in the absence of added buffers, to a reversible down-regulation of O2 production by about 20%. These findings add a previously unidentified component to the regulatory network of oxygenic photosynthesis and conclude the more than 50-y-long quest for the function of CO2/ in photosynthetic water oxidation.
Department of Chemistry, Chemical Biological Centre and Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, S-90187 Umeå, Sweden.
Sergey
S
Koroidov
Dmitriy
D
Shevela
Tatiana
T
Shutova
Göran
G
Samuelsson
Johannes
J
Messinger
D001639:Bicarbonates / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D013058:Mass Spectrometry; D008954:Models, Biological; D009862:Online Systems; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010103:Oxygen Isotopes; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D011522:Protons; D013997:Time Factors; D014867:Water / Q000378:metabolism*
D001639:Bicarbonates; D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D045332:Photosystem II Protein Complex; D011522:Protons; D014867:Water; D002245:Carbon Dioxide; D010100:Oxygen
bicarbonate; carbon dioxide; oxygen evolution; proton release; water splitting