Spectroscopic and Functional Characterization of Iron–Sulfur Cluster-Bound Forms of Azotobacter vinelandiiNifIscA
| Autor: | Sunil G. Naik, Boi Hanh Huynh, Bo Zhang, Michael K. Johnson, Daphne T. Mapolelo |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Iron-Sulfur Proteins
Azotobacter vinelandii Circular dichroism Azotobacter biology Circular Dichroism Iron–sulfur cluster Nitrogenase Plasma protein binding Spectrum Analysis Raman biology.organism_classification Biochemistry Article Dithiothreitol Spectroscopy Mossbauer chemistry.chemical_compound Crystallography Bacterial Proteins chemistry Mössbauer spectroscopy Cluster (physics) Spectrophotometry Ultraviolet Protein Binding |
| Zdroj: | Biochemistry. 51:8071-8084 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of (Nif)IscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV-visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii(Nif)IscA, and the ability of (Nif)IscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that (Nif)IscA can rapidly and reversibly cycle between forms containing one [2Fe-2S](2+) and one [4Fe-4S](2+) cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S](2+) clusters and O(2)-induced [4Fe-4S](2+) oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S](2+)-(Nif)IscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-(Nif)IscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions. |
| Databáze: | OpenAIRE |
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