Structural and spectroscopic analysis of multi-centered metallo enzymes and their functional complexes involved in nitrate- and sulfate-respiration

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Electron transfer processes play a key role in maintaining life. Practically all biological energy conversion systems employ redox cascades. Fe and Cu are among the predominant active centers of proteins involved with mediation and catalysis of these processes. In the project we want to characterize by structural (high-resulation X-ray crystallography) and spectroscopic methodes (EPR/ENDOR, Mössbauer, resonance Raman) several main modules involved in (i) nitrate-ammonification, and (ii) sulfate-respiration. In these processes either nitrate (-» NH3) or sulfate (-» H2S) serve as electron acceptors. Based on the structural and spectroscopic features of these building blocks an electronic and magnetic picture of the active sites will be derived which will help in understanding the function of the catalytic centers within one module, and which will help in defining intra- and intermolecular electron pathways. Main targets will be: (i) the cytochrome c nitrite reductase complex from nitrate-ammonifying bacteria, a multiheme system with novel structural motifs and spectroscopic properties, and (ii) the adenosine-5`-phosphosulfate reductase and the dodecaheme protein from sulfate-reducing bacteria.