Pigment Complexes in Photosynthetic Prokaryotes; Structure and Function
The photosynthetic apparatus of prokaryotes, in contrast to that of higher plants, shows an almost bewildering variety of pigmentation and organization. Nevertheless, as in all photosynthetic organisms, two major functions of the pigments can be discerned. The first one, the so-called antenna function, consists of the absorption of light and the transfer of the energy of the excited pigment molecules to the reaction center. The second, equally important function concerns electron transfer in the reaction center; the primary photochemical reaction consists of the transfer of an electron from an excited chlorophyll or bacteriochlorophyll (BChl) molecule to a neighboring acceptor molecule. Subsequent electron transfer reactions serve to stabilize the energy of the radical pair thus formed and make it available for secondary electron transfer and biosynthetic reactions. More than 90% of the pigments present in photosynthetic organisms have an antenna function only. Originally it was thought that these would be dispersed in the lipid bilayer of the photosynthetic membrane, but nowadays it is firmly established that they are either bound to intrinsic proteins or, as in cyanobacteria and green bacteria, contained in extramembraneous structures, the phycobilisomes and chlorosomes.
KeywordsReaction Center Purple Bacterium Green Sulfur Bacterium Antenna Complex Antenna Function
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- Amesz, J., 1987, Primary electron transport and related processes in green photosynthetic bacteria, Photosynthetica, 21: 225.Google Scholar
- Amesz, J., 1989, Energy transfer and electron transport in Heliobacterium chlorum, Photosynthetica, 23, in press.Google Scholar
- Brune, D.C., Nozawa, T., and Blankenship, R.E., 1987, Antenna organization in the green photosynthetic bacterium Chloroflexus aurantiacus. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in chlorosomes, Biochemistry, 26: 8644.PubMedCrossRefGoogle Scholar
- Deisenhofer, J., Epp, O., Mild, K., Huber, R., and Michel, H., 1984, Structure analysis of a membrane protein complex. Electron density map at 3 A resolution and a model of the chromophores of the photosynthetic reaction center from Rhodopseudomonas viridis, J. Mol. Biol., 180: 385.PubMedCrossRefGoogle Scholar
- Gillbro, T., Sandström, A., Sundström, V., and Olson, J.M., 1988, Picosecond energy transfer kinetics in chlorosomes and bacteriochlorophyll a-proteins of Chlorobium limicola, in: “Green Photosynthetic Bacteria”, J.M. Olson, J.G. Ormerod, J. Amesz, E. Stackebrandt, and H.G. Trüper, eds., Plenum Press, New York, p. 91.CrossRefGoogle Scholar
- Lutz, M., and Van Brakel, G., 1988, Ground-state molecular interactions of the bacteriochlorophyll c in chlorosomes of green bacteria and in model systems: A resonance Raman study, in: “Green Photosynthetic Bacteria”, J.M. Olson, J.G. Ounerod, J. Amesz, E. Stackebrandt, and H.G. Trüper, eds., Plenum Press, New York, p. 23.CrossRefGoogle Scholar
- Olson, J.M., 1989, Chlorophyll organization in green photosynthetic bacteria, Biochim. Biophys. Acta, 549: 33.Google Scholar
- Schirmer, T., Huber, R., Schneider, M., Bode, W., Miller, M., and Hacken, M.L., 1986, Crystal structure analysis and refinement at 2.5 A of hexameric c-phycocyanin from the cyanobacterium Agmenellum quadruplicatum. The molecular model and its implications for light-harvesting, J. Mol. Biol., 188: 651.PubMedCrossRefGoogle Scholar
- Trost, J.T., and Blankenship, R.E., 1990, Isolation of a reaction center particle and a small c-type cytochrome from Heliobacillus mobilis, in: “Proc. 8th Intern. Congr. Photosynthesis, Stockholm, 1989”, Kluwer, Dordrecht, in press.Google Scholar
- Van de Meent, E.J., Kleinherenbrink, F.A.M., and Amesz, J., 1990, Properties of a solubilized and purified antenna-reaction center complex from heliobacteria, in:“ Proc. 8th Intern. Congr. Photosynthesis, Stockholm, 1989”, Kluwer, Dordrecht, in press.Google Scholar
- Van Grondelle, R., and Sundström, V., 1988, Excitation energy transfer in photosynthesis, in: “Photosynthetic light-harvesting systems. Organization and function”, H. Scheer, and S. Schneider, eds., Walter de Gruyter, Berlin, p. 403.Google Scholar