BACKGROUND The sulfur oxygenase reductase (SOR) is the initial enzyme of the sulfur oxidation pathway in the thermoacidophilic Archaeon Acidianus ambivalens. The SOR catalyzes an oxygen-dependent sulfur disproportionation to H(2)S, sulfite and thiosulfate. The spherical, hollow, cytoplasmic enzyme is composed of 24 identical subunits with an active site pocket each comprising a mononuclear non-...

Many systems are available for the production of recombinant proteins in bacterial and eukaryotic model organisms, which allow us to study proteins in their native hosts and to identify protein-protein interaction partners. In contrast, only a few transformation systems have been developed for archaea, and no system for high-level gene expression existed for hyperthermophilic organisms. Recentl...

The 7598-bp plasmid pDL10 from the extremely thermophilic, acidophilic, and chemolithoautotrophic Archaeon Acidianus ambivalens was sequenced. It contains 10 open reading frames (ORFs) organized in five putative operons. The deduced amino acid sequence of the largest ORF (909 aa) showed similarity to bacterial Rep proteins known from phages and plasmids with rolling-circle (RC) replication. Fro...

Sulfide:quinone oxidoreductases (SQR) are ubiquitous membrane-bound flavoproteins involved in sulfide detoxification, in sulfide-dependent energy conservation processes and potenatially in the homeostasis of the neurotransmitter sulfide. The first 2 structures of SQRs from the bacterium Aquifex aeolicus (Marcia et al., Proc Natl Acad Sci USA 2009; 106:9625-9630) and the archaeon Acidianus ambiv...

Analysis of known sulfur oxygenase-reductases (SORs) and the SOR-like sequences identified from public databases indicated that they all possess three cysteine residues within two conserved motifs (V-G-P-K-V-C(31) and C(101)-X-X-C(104); numbering according to the Acidianus tengchongensis numbering system). The thio-modifying reagent N-ethylmaleimide and Zn(2+) strongly inhibited the activities ...

Thermal perturbation of the dicluster ferredoxin from Acidianus ambivalens was investigated employing a toolbox of spectroscopic methods. FTIR and visible CD were used for assessing changes of the secondary structure and coarse alterations of the [3Fe4S] and [4Fe4S] cluster moieties, respectively. Fine details of the disassembly of the metal centers were revealed by paramagnetic NMR and resonan...