Structure at 1.0 Å resolution of a high-potential iron–sulfur protein involved in the aerobic respiratory chain of Rhodothermus marinus
The aerobic respiratory chain of the thermohalophilic bacterium Rhodothermus marinus, a nonphotosynthetic organism from the Bacteroidetes/Chlorobi group, contains a high-potential iron–sulfur protein (HiPIP) that transfers electrons from a bc 1 analog complex to a caa 3 oxygen reductase. Here, we describe the crystal structure of the reduced form of R. marinus HiPIP, solved by the single-wavelength anomalous diffraction method, based on the anomalous scattering of the iron atoms from the [4Fe–4S]3+/2+ cluster and refined to 1.0 Å resolution. This is the first structure of a HiPIP isolated from a nonphotosynthetic bacterium involved in an aerobic respiratory chain. The structure shows a similar environment around the cluster as the other HiPIPs from phototrophic bacteria, but reveals several features distinct from those of the other HiPIPs of phototrophic bacteria, such as a different fold of the N-terminal region of the polypeptide due to a disulfide bridge and a ten-residue-long insertion.
KeywordsHigh-potential iron–sulfur protein Crystal structure Rhodothermus marinus Electron transfer chain
High-potential iron–sulfur protein
Rhodothermus marinus high-potential iron–sulfur protein
Swiss Light Source
Root mean square
We are grateful to Nuno A.M. Félix for excellent technical assistance, to Ana Coelho, from the Mass Spectrometry Service of Instituto de Tecnologia Química e Biológica, and to João Carita for cell growth. We thank Carlos Frazão for advice on high-resolution refinement and the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities. X-ray data collection at SLS was supported by the European Commission under the Sixth Framework Programme through the Key Action: Strengthening the European Research Area, Research Infrastructures, contract no. RII3-CT-2004-506008. This work was supported by Fundação para a Ciência e a Tecnologia (PTDC/BIA-PRO/66833/2006 to M.A., POCTI/BIA-PRO/58608/2004 to M.T., REEQ/336/BIO/05, PTDC/BIA-PRO/67105/2006 to A.M.P.M.). M.S. received a grant from Fundação para a Ciência e a Tecnologia (BPD/24193/2005).
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