The role of metal ions in photosynthesis

1. The role of metal ions in photosynthesis

2. The photosynthesis Solar energy – chemical energy The green plants produce ~ 1 g glucose every hour per square meter of leaf surface. This means that photosynthesis is the highest volume biochemical process in the Earth, as approximately 200 billion ton carbohydrate equivalent is formed per year in this reaction, although only less than 1% of the radiation reached the Earth is utilised in the photosynthesis. ~10 Nobel prize

3. Photosynthesis

4. Photosynthesis

5. Photosynthesis

7. Photosynthesis Absorption of light and transfer in the photosynthetic system – The photosynthetic reaction centres The electron transport chain between the two photosystems Mn-catalysed oxidation of water to dioxygen (OEC) The role of the ribulose 1,5-diphosphate in the photosystem Evolution – vs. Future outlooks

8. Photosynthesis Absorption of light and transfer in the photosynthetic system – The photosynthetic reaction centres The electrontransport chain between the two photosystems Mn-catalysed oxidation of water to dioxygen (OEC) The role of the ribulose-1,5-diphosphate in the photosystem Evolution – vs. Future outlook

9. Photosynthesis – utilization of sunlight

10. Photosynthesis – utilization of sunlight

11. Pigments of photosynthesis Chlorophyll A

12. Pigments of photosynthesis

13. The „antenna” of photosynthesis Structurisation of the pigment materials in the thylakoid membrane in the monomeric antenna complex of the photosystem II (CP43 and CP47 in the antenna complex and D1/D2 in the reaction centre)A and B Figs. show different views. Stroma Lumen Science 2004, 303, 1831

14. The „antenna” of photosynthesis Structurisation of the pigment materials in the thylakoide membrans in the antenna complexes of photosystem I. A and B Figs. show different views. Current Opinion in Structural Biology 2002, 12, 244

15. Transport of the photon energy by resonance transfer

16. The positive characteristics of magnesium ions in the photosynthesis Assure the spatial arrangement of the chlorophyll molecules. The Mg2+-ion is perfect for this role: because its size is optimal to form stable complex with the tetrapyrrole ring, furthermore it prefers to form complexes with coordination number six. The Mg2+ ion forms only weak spin-orbit coupling with the excited state of the tetrapyrrole ring, and thus it hinders the transfer of the energy of light in the forms of fluorescence or heat. The Mg2+ ion in contrast with most of the transition metal ions can not redox react with the surronding ligands and thus the photosynthetic reaction centres are defended from the unwanted irreversible decomposition.

17. Photosynthesis - photosystems

18. Photosynthesis - photosystems

19. Photosyntesis – photosystems II Structurisation of the PS II dimer pigment-protein complex in the thylakoid membrane Science 2004, 303, 1831

20. ATP synthesis

21. Photosynthesis Absorption of light and transfer in the photosystem – The photosynthetic reaction centres The electron transport chain between the two photosystems Mn catalysed oxidation of water to dioxygen (OEC) The role of ribulose 1,5-diphosphate in the photosystem Evolution – vs. Future outlook

22. Electrontransfer metalloproteins 1.) Iron-sulphur proteins (Ferredoxin):

23. Electrontransfer metalloproteins 2.) Cytochromes: Hem a Hem c Cytochrome c

24. Electrontransfer metalloproteins 3.) Blue copper proteins (Plastocyanin):

25. The photosynthetic electron transport Z scheme

26. Elements of the photosynthetic electrontransport bicarbonate Relative arrangement of the molecules participating in the primary electrontransport processes of PS II system. Science 2004, 303, 1831

27. Elements of the photosynthetic electron transport Schematic picture of the b6f complex of the eucaryota photosynthetic electrontransport system.

28. The long range electron transfer and transport systems Schematic picture of a part of the eucariote photosynthetic electrontransport system (cytochrome f → plastocyanin → P700).

29. Reduction of NADP+ +H+ +2e-

30. Photosynthesis Absorption of light and transfer in the photosystem – The photosynthetic reaction centres The electron transport chain between the two photosystems Mn-catalysed oxidation of water to dioxygen (OEC) The role of ribulose 1,5 diphosphate in photosystem Evolution – vs. Future outlook

31. Oxidation of water

32. Oxidation of water +1,2

33. Suggested structures of the OEC (WOC) Coordination Chemistry Reviews 2008, 252

34. OEC models from the same X-ray structures (B) (A) Coordination Chemistry Reviews 2008, 252

35. Schematic figure of the OEC catalytic centre The amino acids indicated by different colours belong to different protein subunits: yellow - D1, orange - D2 and green - CP43. Science 2004, 303, 1831

36. Schematic figure of oxidation of the water OEC (Oxygen Evolving Complex): The lifetime, the composition of the complex and evolution of protons and electrons in the oxidation steps of water.

37. A proposed mechanism of the stepwise oxidation of water (The question marks indicates that the Mn-Mn distances are not known.) Chemical Reviews 1996, 96, 2947

38. A proposed mechanism of the stepwise oxidation of water Biochimica et Biophysica Acta 2001, 1503

39. A proposed mechanism of the stepwise oxidation of water Coordination Chemistry Reviews 2008, 252

40. Proposed structure of OEC (WOC) - 2011 Nature 2011, 473, 55

41. Favourable characteristics of the manganase ions in the photosynthesis (i) Versatility in the stable or metastable oxidation states of manganese: MnII, MnIII, MnIV, MnVI, MnVII. (ii) Labile coordination of the ligands. (iii) Propensity to form high spin complexes. (iv) The freshly formed mixed valence oxides MnO2–x×nH2O catalyses efficiently the disproportionation of hydrogene-peroxide, in which oxygen is also formed. Such oxide-hydroxide compounds might also be present, when photosynthesis was evolved. (v) Besides the metabolism of oxygen, the Mnn+ ions occur in other enzymes, such as the Mn containing superoxide dismutases as well as catalases and peroxidases.

42. Hydrophil and hydrophob channels around the OEC (3) (2) (1) 1. O2 channel; 2and 3. hydrophil channels for the substrate and the proton. Coordination Chemistry Reviews 2008, 252

43. Modeling the water flow around the OEC Biochemistry, 2010, 49, 1873

44. Photosynthesis Absorption of light and transfer in the photosystem – The photosynthetic reaction centre The electron transport chain between the two photosystems Mn catalysed oxidation of water to dioxygen (OEC) The role of ribulose 1,5-diphosphate in the photosystem Evolution – vs. Future outlook

45. Reactions of the dark process

46. Reactions of the dark process Schematic picture of the CO2 fixation catalysed by ribulose 1,5 diphosphate carboxylase enzyme.

47. Reactions of the dark process Schematic picture of the CO2 fixation catalysed by ribulose 1,5 diphosphate carboxylase enzyme.

48. Structure of the ribulose 1,5 diphosphate carboxylase X-ray structure of the ribulose 1,5-diphosphate carboxylase enzyme C. Reinhardtii green algae. The L subunits are indicated by blue and green, while the S subunits by yellow colour. Journal of Molecular Biology 2002, 316, 679

49. Active centre of the ribulose 1,5-diphosphate carboxylase Active centre of the ribulose 1,5-diphosphate carboxylase enzyme of C. Reinhardtii green algae in the presence of a model substrate. Journal of Molecular Biology 2002, 316, 679

50. Photosynthesis Absorption of light and transfer in the photosystem – The photosynthetic reaction centre The electron transport chain between the two photosystems Mn catalysed oxidation of water to dioxygen (OEC) The role of ribulose 1,5-diphosphate in the photosystem Evolution – vs. Future outlook