Diiron metalloprotein

A rationally designed four-helix bundle diiron metalloprotein was shown by... 

Tshuva, E. Y. Lippard, S. J. Synthetic models for non-heme carboxylate-bridged diiron metalloproteins strategies and tactics. Chem. Rev. 2004, 104, 987-1012. 

The goal of diiron model chemistry is to develop small molecule systems that accurately reproduce spectroscopic, structural, and more ambitiously, reactivity aspects of diiron metalloproteins. Despite being structurally similar, diiron enzymes carry out a variety of catalytic processes see Iron Proteins with Dinuclear Active Sites). Advancements in the synthesis and characterization of small molecule mimics for nonheme diiron enzymes have been tremendous in the last decade. Biomimetic studies have been carried out in efforts to reproduce the structural and functional aspects of these biocatalysts. Although this has been a challenging endeavor, much information regarding the structural and mechanistic aspects of catalytic intermediates has been obtained. 

A new member of the family of nonheme diiron enzymes recently discovered is called rubrerythrin. This metalloprotein is formally classified as an oxidoreductase (rubredoxin oxygen oxidoreductase). The diiron(III,III) active site structure is displayed in Figure 2(f). This biomolecule possesses two histidines coordinated to one iron and one histidine coordinated to the second iron. A carboxylate bridges the two irons and there are carboxylate ligands also coordinated to each iron. The purpose of this enzyme in the strict anaerobe is to safely reduce oxygen to water. 

S. P. Watton, A. Masschelein, J. Rebek Jr., and S. J. Lippard. Synthesis and characterization of a bioinorganic chip for the carboxylate-bridged ( i-oxo)diiron(III) metalloprotein core, submitted for publication. 

Lombardi A, Summa CM, Geremia S, Randaccio L, Pavone V, DeGrado WF. 2000. Retrostructural analysis of metalloproteins application to the design of a minimal model for diiron proteins. Proc Natl Acad Sci USA 97 6298-6305. 

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