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Model of the MitoNEET [2Fe-2S] Cluster Shows Proton Coupled Electron Transfer.


ABSTRACT: MitoNEET is an outer membrane protein whose exact function remains unclear, though a role of this protein in redox and iron sensing as well as in controlling maximum mitochondrial respiratory rates has been discussed. It was shown to contain a redox active and acid labile [2Fe-2S] cluster which is ligated by one histidine and three cysteine residues. Herein we present the first synthetic analogue with biomimetic {SN/S2} ligation which could be structurally characterized in its diferric form, 52-. In addition to being a high fidelity structural model for the biological cofactor, the complex is shown to mediate proton coupled electron transfer (PCET) at the {SN} ligated site, pointing at a potential functional role of the enzyme's unique His ligand. Full PCET thermodynamic square schemes for the mitoNEET model 52- and a related homoleptic {SN/SN} capped [2Fe-2S] cluster 42- are established, and kinetics of PCET reactivity are investigated by double-mixing stopped-flow experiments for both complexes. While the N-H bond dissociation free energy (BDFE) of 5H2- (230 ± 4 kJ mol-1) and the free energy ?G°PCET for the reaction with TEMPO (-48.4 kJ mol-1) are very similar to values for the homoleptic cluster 4H2- (232 ± 4 kJ mol-1, -46.3 kJ mol-1) the latter is found to react significantly faster than the mitoNEET model (data for 5H2-: k = 135 ± 27 M-1 s-1, ?H‡ = 17.6 ± 3.0 kJ mol-1, ?S‡ = -143 ± 11 J mol-1 K-1, and ?G‡ = 59.8 kJ mol-1 at 293 K). Comparison of the PCET efficiency of these clusters emphasizes the relevance of reorganization energy in this process.

SUBMITTER: Bergner M 

PROVIDER: S-EPMC5812485 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Model of the MitoNEET [2Fe-2S] Cluster Shows Proton Coupled Electron Transfer.

Bergner Marie M   Dechert Sebastian S   Demeshko Serhiy S   Kupper Claudia C   Mayer James M JM   Meyer Franc F  

Journal of the American Chemical Society 20170105 2


MitoNEET is an outer membrane protein whose exact function remains unclear, though a role of this protein in redox and iron sensing as well as in controlling maximum mitochondrial respiratory rates has been discussed. It was shown to contain a redox active and acid labile [2Fe-2S] cluster which is ligated by one histidine and three cysteine residues. Herein we present the first synthetic analogue with biomimetic {SN/S<sub>2</sub>} ligation which could be structurally characterized in its diferri  ...[more]

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