AI Article Synopsis
- The crystal structure of SoxF, an archaeal Rieske iron-sulfur protein from Sulfolobus acidocaldarius, was solved with high resolution using multiple wavelength anomalous dispersion (MAD).
- SoxF is part of the SoxM supercomplex on the plasma membrane, which features both cytochrome bc(1) and cytochrome c oxidase characteristics, and plays a role in electron transfer during caldariella quinone oxidation.
- Although SoxF shares similarities in the [2Fe-2S] cluster with eucaryal Rieske proteins, its overall structure exhibits significant divergence, indicating adaptations for the extreme conditions in its hyperthermo-acidophilic environment.
Article Abstract
The first crystal structure of an archaeal Rieske iron-sulfur protein, the soluble domain of Rieske iron-sulfur protein II (soxF) from the hyperthermo-acidophile Sulfolobus acidocaldarius, has been solved by multiple wavelength anomalous dispersion (MAD) and has been refined to 1.1 A resolution. SoxF is a subunit of the terminal oxidase supercomplex SoxM in the plasma membrane of S. acidocaldarius that combines features of a cytochrome bc(1) complex and a cytochrome c oxidase. The [2Fe-2S] cluster of soxF is most likely the primary electron acceptor during the oxidation of caldariella quinone by the cytochrome a(587)/Rieske subcomplex. The geometry of the [2Fe-2S] cluster and the structure of the cluster-binding site are almost identical in soxF and the Rieske proteins from eucaryal cytochrome bc(1) and b(6)f complexes, suggesting a strict conservation of the catalytic mechanism. The main domain of soxF and part of the cluster-binding domain, though structurally related, show a significantly divergent structure with respect to topology, non-covalent interactions and surface charges. The divergent structure of soxF reflects a different topology of the soxM complex compared to eucaryal bc complexes and the adaptation of the protein to the extreme ambient conditions on the outer membrane surface of a hyperthermo-acidophilic organism.
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