Proteins, glycerolipids and carotenoids in the functional photosystem II architecture
Ozge Sozer1, Mihaly Kis1, 4, Zoltan Gombos 1, Bettina Ughy1
1
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary
TABLE OF CONTENTS
- 1. Abstract
- 2. Introduction
- 3. Lipid driven construction of the PSII complex
- 3.1. In vitro studies
- 3.2. The structural role of the anionic lipids PG and SQDG in eukaryotes, higher plants and green algae.
- 3.3. Structural importance of glycerolipids in the architecture of PSII in cyanobacteria
- 3.3.1. The involvement of DGDG in the construction of cyanobacterial PSII
- 3.3.2. The role of PG in the assembly of photosynthetic complexes
- 4. How do glycerolipids affect PSII processes
- 4.1. Functioning proteins and glycerolipids are the bricks and mortar in constructing the PSII architecture
- 4.2. The functional role of lipid molecules in the PSII of plants and algae
- 4.2.1. The involvement of MGDG in photosynthesis-related processes
- 4.2.2. The role of DGDG in photosynthetic processes
- 4.2.3. The role of SQDG in the photosynthetic function of PSII
- 4.2.4. PG depletion affects photosynthetic activities
- 4.3. The functional role of lipid molecules in the PSII of cyanobacteria
- 4.3.1. The role of DGDG in photosynthetic processes
- 4.3.2. The involvement of SQDG in photosynthesis
- 4.3.3. PG: an indispensable lipid component of photosynthetic complexes
- 5. The structural involvement of carotenoids in the PSII complex
- 5.1. The structural importance of carotenoids in the PSII of higher plants and algae
- 5.2. The contribution of carotenoids to the formation of cyanobacterial PSII complexes
- 6. Carotenoids - regulatory components in oxygenic photosynthesis
- 6.1. The functional importance of carotenoids in higher plants and algae
- 6.2. The functional roles of carotenoids in Cyanobacteria
- 6.2.1. Carotenoids: protective agents
- 6.2.2. The Orange Carotenoid Protein and non photochemical quenching of PSII in cyanobacteria
- 7. Perspectives
- 8. Acknowledgements
- 9. References
1. ABSTRACT
Photosystem II (PSII), the first supercomplex of the electron transport chain, governs the energy transfer using harvested light energy, which is transformed into biochemical energy. Phosphatidylglycerol and sulfoquinovosyl diacylglycerol, the anionic lipids of photosynthetic organisms, together with a neutral lipid, digalactosyldiacylglycerol, assist in the assembly of photosynthetic complexes. These lipids and carotenoids serve as mortar for the proteins which act as bricks in the construction of the active photosynthetic machinery, and they have determinative roles in the oligomerization of protein subunits. X-ray crystallographic localization of glycerolipids and carotenoids revealed that they are present at functionally and structurally important sites of both the PSI and PSII reaction centers. Phosphatidylglycerol is involved in the formation of the reaction-center oligomers and controls electron transport at the acceptor site of PSII. Digalactosyldiacylglycerol, together with phosphatidylglycerol, is involved in the electron transport at the donor site. Phosphatidylglycerol and carotenoids are needed to glue CP43 to the reaction center core. Carotenoids are protective agents, which prevent photosynthetic complexes from degradation caused by reactive oxygen species.
