Spectopotentiometric properties and salt-dependent thermotolerance of a [2Fe-2S] ferredoxin-involved nitrate assimilation in Haloferax mediterranei

Martinez-Espinosa, R.M., Richardson, D.J., Butt, J.N. and Bonete, M.J. (2007) Spectopotentiometric properties and salt-dependent thermotolerance of a [2Fe-2S] ferredoxin-involved nitrate assimilation in Haloferax mediterranei. FEMS Microbiology Letters, 277 (1). pp. 50-55. ISSN 1574-6968

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Abstract

Haloferax mediterranei is a halophilic archaeon that can grow using nitrate as the sole nitrogen source. A ferredoxin that serves as the physiological electron donor to the nitrate and nitrite reductases in this assimilatory process has been characterized. The ferredoxin was found to contain approximately two atoms of iron and two atoms of sulphur, indicative of the binding of a [2Fe–2S] cluster. The electron paramagnetic resonance spectrum of the reduced form of the protein displayed a rhombic signal, with gx=1.91, gy=1.98, gz=2.07, that shows considerable similarity to plant and algal [2Fe–2S] ferredoxins. UV-visible spectropotentiometric analysis determined a midpoint redox potential for the [2Fe–2S]2+/1+ transition of around -285 mV vs. SHE that was independent of salt concentration. UV-visible spectroscopy was also used to establish that the [2Fe–2S] cluster integrity of this protein was maintained over the pH range 5–11. Significantly, the Haloferax mediterranei ferredoxin was shown to be a highly thermostable protein. It was stable up to 60 °C in a low-salt (0.2 M) medium and this increased to 80 °C in a high-salt (4 M) medium. This thermostability at high salt concentration is an essential physiological characteristic because haloarchaea are mainly found in environments where high temperatures and concentrated salt water occur.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
Related URLs:
Depositing User: Rachel Smith
Date Deposited: 17 Feb 2011 16:10
Last Modified: 24 Jul 2019 15:20
URI: https://ueaeprints.uea.ac.uk/id/eprint/21402
DOI: 10.1111/j.1574-6968.2007.00942.x

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