Dinuclear site carriers

The iron ligands in the dinuclear sites of these proteins are very similar — the structures of the (p-carboxylato) di-iron cores found for MMOH, ToMOH, RNR-R2, rubreythrin, stearoyl-acyl carrier protein A desaturases, bacterioferritin, and methaemerythrin are presented in Figure 13.26. They all have the same three-amino-acid structural motif on one side of the di-iron site, made up of a bridging Glu and two His residues, coordinated in... 

Proteins with dinuclear iron centres comprise some well studied representatives like ribonucleotide reductase (RNR), purple acid phosphatase (PAP), methane monooxygenase hydroxylase (MMOH), ruberythrin and hemerythrin. The latter is an oxygen carrier in some sea worms it has been first characterized within this group and has thus laid the foundation to this class of iron coordination motif. Ruberythrin is found in anaerobic sulfate-reducing bacteria. Its name implies that, in addition to a hemerythrin-related diiron site another iron is coordinated in a mononuclear fashion relating to rubredoxin which is an iron-... 

Nature sometimes solves identical problems with apparently quite different solutions. Important examples of such a convergent evolution at the molecular level are the functional parallels between iron and copper centers in bioinorganic chemistry. The dioxygen-carrier proteins of different organisms may, for instance, be based on mononuclear iron tetrap5rrrole complexes or in contrast may involve dinuclear copper sites 10). S5mthetic chemistry can even go a step fiuther and try to mimic basic... 

Oxidative transformations carried out by the reaction of copper(I) and O2 in Nature are widespread in terms of the variety of substrates and in copper active-site structures. The archetype for dicopper-dioxygen activation has been the dioxygen carrier for arthropods and mollusks, hemocyanin (He), which has a dinuclear copper(I) active site where the copper centers are ca. 

Spectroscopic and biochemical studies reveal that the active site of tyrosinase is very similar to the dinuclear copper site in hemocyanins (Hcs) (13), which are dioxygen carriers in the hemolymph of mollusks and arthropods. 

Tyrosinase is the oldest known monooxygenase that catalyzes monophenol oxidation to quinone [34, 109]. It contains a dinuclear copper site which is very similar to that found in hemocyanin, a ubiquitous oxygen carrier for invertebrates [110-112]. The dioxygen adduct of tyrosinase is known to exhibit unusual spectral characteristics which are similar to those of the dioxygen adduct of hemocyanin (1) unusually low v(O-O) assignable to a symmetric peroxide ascertained by resonance Raman spectroscopy [113], (2) unique intense absorption bands seen at 350 nm ( , -20000 cm M ) / 2Cu and ca. 580 nm... 

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