Photosynthetic bacteria reaction center

Despite considerable efforts very few membrane proteins have yielded crystals that diffract x-rays to high resolution. In fact, only about a dozen such proteins are currently known, among which are porins (which are outer membrane proteins from bacteria), the enzymes cytochrome c oxidase and prostaglandin synthase, and the light-harvesting complexes and photosynthetic reaction centers involved in photosynthesis. In contrast, many other membrane proteins have yielded small crystals that diffract poorly, or not at all, using conventional x-ray sources. However, using the most advanced synchrotron sources (see Chapter 18) it is now possible to determine x-ray structures from protein crystals as small as 20 pm wide which will permit more membrane protein structures to be elucidated. 

The interiors of rhodopseudomonad bacteria are filled with photosynthetic vesicles, which are hollow, membrane-enveloped spheres. The photosynthetic reaction centers are embedded in the membrane of these vesicles. One end of the protein complex faces the Inside of the vesicle, which is known as the periplasmic side the other end faces the cytoplasm of the cell. Around each reaction center there are about 100 small membrane proteins, the antenna pigment protein molecules, which will be described later in this chapter. Each of these contains several bound chlorophyll molecules that catch photons over a wide area and funnel them to the reaction center. By this arrangement the reaction center can utilize about 300 times more photons than those that directly strike the special pair of chlorophyll molecules at the heart of the reaction center. 

Michel, H., Deisenhofer, J. Relevance of the photosynthetic reaction center from purple bacteria to the structure of photosystem II. BicKhemistry 27 1-7, 1988. 

Norris, J.R., Schiffer, M. Photosynthetic reaction centers in bacteria. Chem. Eng. News 68(31) 22-37, 1990. 

The photosynthetic reaction center (RC) of purple nonsulfur bacteria is the core molecular assembly, located in a membrane of the bacteria, that initiates a series of electron transfer reactions subsequent to energy transfer events. The bacterial photosynthetic RCs have been characterized in more detail, both structurally and functionally, than have other transmembrane protein complexes [1-52]. 

Deisenhofer, J. Michel, H. (1991) Structures of bacterial photosynthetic reaction centers. Annu. Rev. Cell Biol. 7, 1-23. Description of the structure of the reaction center of purple bacteria and implications for the function of bacterial and plant reaction centers. 

Wavepacket motion is now routinely observed in systems ranging from the very simple to the very complex. In the latter category, we note that coherent vibrational motion on functionally significant time scales has been observed in the photosynthetic reaction center [15], bacteriorhodopsin [16], rhodopsin [17], and light-harvesting antenna of purple bacteria (LH1) [18-20]. Particularly striking are the results of Zadoyan et al. [21] on the... 

Photoautotrophic bacteria 8 Photofootprinting 266 Photorespiration 707 Photosynthesis 506,517, 705 Photosynthetic bacteria 7 Photosynthetic phosphorylation 303, 517 Photosynthetic reaction centers 71 Phthaldialdehyde 120s Phycoerythrin 22 Phycomycetes 20... 

Bacterial photosynthesis. What is the relationship of the Z scheme of Fig. 23-17 to bacterial photosyntheses In photoheterotrophs, such as the purple Rhodospirillum, organic compounds, e.g., succinate, serve as electron donors in Eq. 23-30. Because they can utilize organic compounds for growth, these bacteria have a relatively low requirement for NADPH or other photochemically generated reductants and a larger need for ATP. Their photosynthetic reaction centers receive electrons via cytochrome c from succinate (E° ... 

Woodbury, N. W., M. Becker, D. Middendorf, and W. W. Parson, Picosecond kinetics of the initial photochemical electron transfer reaction in bacterial photosynthetic reaction centers. Biochem. 24 7516, 1985. Fast spectrophotometric techniques are used to follow the initial steps in reaction centers purified from photosynthetic bacteria. 

The energy collected by the LH II antenna is transferred to another antenna complex known as LH I, which surrounds the RC. The photosynthetic reaction centers of bacteria consist mainly of a protein that is embedded in and spans a lipid bilayer membrane. In the reaction center, a series of electron transfer reactions are driven by the captured solar energy. These electron transfer reactions convert the captured solar energy to chemical energy in the... 

The observation of a photosynthetic reaction center in green sulfur bacteria dates back to 1963.39 Green sulfur bacteria RCs are of the type I or the Fe-S-type (photosystem I). Here the electron acceptor is not the quinine instead, chlorophyll molecules (BChl 663, 81 -OII-Chi a, or Chi a) serve as primary electron acceptors, and three Fe4S4 centers (ferredoxins) serve as secondary acceptors. A quinone molecule may or may not serve as an intermediate carrier between the primary electron acceptor (Chi) and the secondary acceptor (Fe-S centers).40 The process sequence leading to the energy conversion in RCI is shown in Figure 21. 

See, e.g., J. Deisenhofer, H. Michel, The Photosynthetic Reaction Center from the Purple Bacterium Rhodopseudomonas-Viridis. Science 1989, 245, 1463-1473 M. E. Michel-Beyerle, M. Plato, J. Deisenhofer, H. Michel, M. Bixton, J. Jortner, Unidirectionality of Charge Separation in Reaction Centers of Photosynthetic Bacteria. Biochim. Biophys. Acta 1988, 932, 52-70. 

In green plants and certain algae, the photosynthetic machinery is elaborated over those found in purple bacteria and is now able to reach the high potentials needed to oxidize water to dioxygen. This oxygenic photosystem is comprised of two photosynthetic reaction centers (sensitizer assemblies), photosystem I (PS I) and... 

DiMagno, T. J., and Norris, J. R., 1993, Initial electron transfer events in photosynthetic bacteria. In The Photosynthetic Reaction Center, (J. Deisenhofer and J. R. Norris, eds.) Volume 2, pp. 1059132, Academic Press, San Diego, USA. 

Takahashi, E., and Wraight, C. A., 1994, Molecular genetic manipulation and characterization of mutant photosynthetic reaction centers from purple non-sulphur bacteria. In Advances in Molecular and Cell Biology Molecular Processes in Photosynthesis, (J. Barber, ed.)... 

C. R. D. Lancaster and H. Michel, in Photosynthetic Reaction Centers of Purple Bacteria, in Handbook of MetaUoproteins , eds. A. Messerschmidt, R. Huber, T. Poulos, and K. Wieghardt, John Wiley Sons, New York, 2001, p. 119. 

Photosynthetic Bacteria and the Photosynthetic Reaction Centers of Green Plants Have a Common Core... 

Hartmut was able to grow crystals of bacteriorhodopsin but they were not suitable for X-ray crystallography for various reasons. He went to scientific meetings where people interested in membrane proteins came together and at one of these meetings he heard about photosynthetic reaction centers and about purification protocols available at that time, and the big advantages that the purple bacteria can provide. Under certain conditions their membranes are filled with photosynthetic reaction centers. Thus you can have a good source of protein, which is extremely important. He tried to work with them and soon he had success. 

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