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Assembly of nonheme Mn/Fe active sites in heterodinuclear metalloproteins.

ABSTRACT: The ferritin superfamily contains several protein groups that share a common fold and metal coordinating ligands. The different groups utilize different dinuclear cofactors to perform a diverse set of reactions. Several groups use an oxygen-activating di-iron cluster, while others use di-manganese or heterodinuclear Mn/Fe cofactors. Given the similar primary ligand preferences of Mn and Fe as well as the similarities between the binding sites, the basis for metal specificity in these systems remains enigmatic. Recent data for the heterodinuclear cluster show that the protein scaffold per se is capable of discriminating between Mn and Fe and can assemble the Mn/Fe center in the absence of any potential assembly machineries or metal chaperones. Here we review the current understanding of the assembly of the heterodinuclear cofactor in the two different protein groups in which it has been identified, ribonucleotide reductase R2c proteins and R2-like ligand-binding oxidases. Interestingly, although the two groups form the same metal cluster they appear to employ partly different mechanisms to assemble it. In addition, it seems that both the thermodynamics of metal binding and the kinetics of oxygen activation play a role in achieving metal specificity.

SUBMITTER: Griese JJ

PROVIDER: S-EPMC4118035 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Assembly of a heterodinuclear Mn/Fe cofactor is coupled to tyrosine-valine ether cross-link formation in the R2-like ligand-binding oxidase.

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Project description: Not available

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Project description:Bimetallic complexes are important sites in metalloproteins but are often difficult to prepare synthetically. We have previously introduced an approach to form discrete bimetallic complexes with MII-(μ-OH)-FeIII (MII = Mn, Fe) cores using the tripodal ligand N,N',N″-[2,2',2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido) ([MST]3-). This series is extended to include the rest of the late 3d transition metal ions (MII = Co, Ni, Cu, Zn). All of the bimetallic complexes have similar spectroscopic and structural properties that reflect little change despite varying the MII centers. Magnetic studies performed on the complexes in solution using electron paramagnetic resonance spectroscopy showed that the observed spin states varied incrementally from S = 0 through S = 5/2; these results are consistent with antiferromagnetic coupling between the high-spin MII and FeIII centers. However, the difference in the MII ion occupancy yielded only slight changes in the magnetic exchange coupling strength, and all complexes had J values ranging from +26(4) to +35(3) cm-1.

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| S-EPMC5680038 | biostudies-literature

Heterodinuclear Mg(II)M(II) (M=Cr, Mn, Fe, Co, Ni, Cu and Zn) Complexes for the Ring Opening Copolymerization of Carbon Dioxide/Epoxide and Anhydride/Epoxide.

Project description:The catalysed ring opening copolymerizations (ROCOP) of carbon dioxide/epoxide or anhydride/epoxide are controlled polymerizations that access useful polycarbonates and polyesters. Here, a systematic investigation of a series of heterodinuclear Mg(II)M(II) complexes reveals which metal combinations are most effective. The complexes combine different first row transition metals (M(II)) from Cr(II) to Zn(II), with Mg(II); all complexes are coordinated by the same macrocyclic ancillary ligand and by two acetate co-ligands. The complex syntheses and characterization data, as well as the polymerization data, for both carbon dioxide/cyclohexene oxide (CHO) and endo-norbornene anhydride (NA)/cyclohexene oxide, are reported. The fastest catalyst for both polymerizations is Mg(II)Co(II) which shows propagation rate constants (kp ) of 34.7 mM-1 s-1 (CO2 ) and 75.3 mM-1 s-1 (NA) (100 °C). The Mg(II)Fe(II) catalyst also shows excellent performances with equivalent rates for CO2 /CHO ROCOP (kp =34.7 mM-1 s-1 ) and may be preferable in terms of metallic abundance, low cost and low toxicity. Polymerization kinetics analyses reveal that the two lead catalysts show overall second order rate laws, with zeroth order dependencies in CO2 or anhydride concentrations and first order dependencies in both catalyst and epoxide concentrations. Compared to the homodinuclear Mg(II)Mg(II) complex, nearly all the transition metal heterodinuclear complexes show synergic rate enhancements whilst maintaining high selectivity and polymerization control. These findings are relevant to the future design and optimization of copolymerization catalysts and should stimulate broader investigations of synergic heterodinuclear main group/transition metal catalysts.

| S-EPMC9306976 | biostudies-literature

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