BIBLIOS

Document type
Journal articles

Document subtype
Full paper

Title
Role of a novel disulfide bridge within the all-beta fold of soluble Rieske proteins

Participants in the publication
Hugo M. Botelho (Author)
Sónia S. Leal (Author)
Andreas Veith (Author)
Vesna Prosinecki (Author)
Christian Bauer (Author)
Renate Fröhlich (Author)
Arnulf Kletzin (Author)
Cláudio M. Gomes (Author)
Dep. Química e Bioquímica
BioISI

Summary
Rieske proteins and Rieske ferredoxins are present in the three domains of life and are involved in a variety of cellular processes. Despite their functional diversity, these small Fe–S proteins contain a highly conserved all-β fold, which harbors a [2Fe–2S] Rieske center. We have identified a novel subtype of Rieske ferredoxins present in hyperthermophilic archaea, in which a two-cysteine conserved SKTPCX(2–3)C motif is found at the C-terminus. We establish that in the Acidianus ambivalens representative, Rieske ferredoxin 2 (RFd2), these cysteines form a novel disulfide bond within the Rieske fold, which can be selectively broken under mild reducing conditions insufficient to reduce the [2Fe–2S] cluster or affect the secondary structure of the protein, as shown by visible circular dichroism, absorption, and attenuated total reflection Fourier transform IR spectroscopies. RFd2 presents all the EPR, visible absorption, and visible circular dichroism spectroscopic features of the [2Fe–2S] Rieske center. The cluster has a redox potential of +48 mV (25 °C and pH 7) and a pK a of 10.1 ± 0.2. These shift to +77 mV and 8.9 ± 0.3, respectively, upon reduction of the disulfide. RFd2 has a melting temperature near the boiling point of water (T m = 99 °C, pH 7.0), but it becomes destabilized upon disulfide reduction (ΔT m = −9 °C, ΔC m = −0.7 M guanidinium hydrochloride). This example illustrates how the incorporation of an additional structural element such as a disulfide bond in a highly conserved fold such as that of the Rieske domain may fine-tune the protein for a particular function or for increased stability.


Institution
INSTITUTO DE TECNOLOGIA QUÍMICA E BIOLÓGICA

Where published
JBIC Journal of Biological Inorganic Chemistry

Publication Identifiers
ISSN - 0949-8257
eISSN - 1432-1327

Publisher
Springer Science and Business Media LLC



Document Identifiers
DOI - https://doi.org/10.1007/s00775-009-0596-3
URL - http://dx.doi.org/10.1007/s00775-009-0596-3

Keywords
Rieske ferredoxin Iron–sulfur cluster Disulfide Protein stability Thermophile