Publications des scientifiques de l'IRD

Nilsson H., Cournac Laurent, Rappaport F., Messinger J., Lavergne J. (2016). Estimation of the driving force for dioxygen formation in photosynthesis. Biochimica et Biophysica Acta-Bioenergetics, 1857 (1), p. 23-33. ISSN 0005-2728.

Titre du document
Estimation of the driving force for dioxygen formation in photosynthesis
Année de publication
2016
Type de document
Article référencé dans le Web of Science WOS:000366771700004
Auteurs
Nilsson H., Cournac Laurent, Rappaport F., Messinger J., Lavergne J.
Source
Biochimica et Biophysica Acta-Bioenergetics, 2016, 1857 (1), p. 23-33 ISSN 0005-2728
Photosynthetic water oxidation to molecular oxygen is carried out by photosystem II (PSII) over a reaction cycle involving four photochemical steps that drive the oxygen-evolving complex through five redox states S-i (i = 0, ... , 4). For understanding the catalytic strategy of biological water oxidation it is important to elucidate the energetic landscape of PSII and in particular that of the final S-4 --> S-0 transition. In this short-lived chemical step the four oxidizing equivalents accumulated in the preceding photochemical events are used up to form molecular oxygen, two protons are released and at least one substrate water molecule binds to the Mn4CaO5 cluster. In this study we probed the probability to form S-4 from S-0 and O-2 by incubating YD-less PSII in the S-0 state for 2-3 days in the presence of O-18(2) and (H2O)-O-16. The absence of any measurable O-16,18(2) formation by water-exchange in the S-4 state suggests that the S-4 state is hardly ever populated. On the basis of a detailed analysis we determined that the equilibrium constant K of the S-4 --> S-0 transition is larger than 1.0 x 10(7) so that this step is highly exergonic. We argue that this finding is consistent with current knowledge of the energetics of the S-0 to S-4 reactions, and that the high exergonicity is required for the kinetic efficiency of PSII.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020] ; Limnologie biologique / Océanographie biologique [034]
Localisation
Fonds IRD [F B010066005]
Identifiant IRD
fdi:010066005
Contact