Amino acid, accumulation arrangement

The function of photosynthetic bacterial reaction centers (RCs) is closely related to their structure. In the last 15 years a wealth of structural data has been accumulated on bacterial RCs, mainly through X-ray structure analysis of three-dimensional RC crystals. In this chapter, the arrangement of protein subunits and cofactors in the RC complexes ofthe non-sulfur purple bucienn Rhodobacter (Rb.) sphaeraides mARhodopseudomonas (Rp.) viridis are delineated. A prominent feature ofthe bacterial RCs is their location in the photosynthetic membrane. Inside the RC complex, a finely tuned arrangement of amino acid residues and cofactors maintains a highly ordered system. The positions and likely functions of hydrogen bonds are described, since they play a key role in protein-cofactor interactions. Special emphasis is placed on the symmetry relations in the RC and on the functional asymmetry of electron and proton transfer that contradicts the observed pseudo two-fold structural symmetry. 

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