A dissimilatory sirohaem-sulfite-reductase-type protein from the hyperthermophilic archaeon Pyrobaculum islandicum

Abstract

A sulf ite-reductase-type protein was purified from the hyperthermophilic crenarchaeote Pyrobaculum islandicum grown chemoorganoheterotrophically with thiosulfate as terminal electron acceptor. In common with dissimilatory sulfite reductases the protein has an a#* structure and contains high-spin sirohaem, non-haem iron and acid-labile sulfide. The oxidized protein exhibits absorption maxima a t 280,392, 578 and 710 nm with shoulders a t 430 and 610 nm. The isoelectric point of pH 8 4 sets the protein apart from all dissimilatory sulfite reductases characterized thus far. The genes for the a-and P-subunits (dsrA and dsrB) are contiguous in the order dsrAdsrB and most probably comprise an operon with the directly following dsrG and dsrC genes. dsrG and dsrC encode products which are homologous to eukaryotic glutathione S-transferases and the proposed y-subunit of Desulfovibrio vulgaris sulf ite reductase, respectively. dsrA and dsrB encode 44.2 kDa and 41.2 kDa peptides which show significant similarity to the two homologous subunits DsrA and DsrB of dissimilatory sulfite reductases. Phylogenetic analyses indicate a common protogenotic origin of the P. islandicum protein and the dissimilatory sulfite reductases from sulfate-reducing and sulfideoxidizing prokaryotes. However, the protein from P. islandicum and the sulfite reductases f rom sulfate-reducers and from sulf ur-oxidizers most probably evolved into three independent lineages prior to divergence of archaea and bacteria.

Phylogeny of the alpha and beta subunits of the dissimilatory adenosine-5′-phosphosulfate (APS) reductase from sulfate-reducing prokaryotes – origin and evolution of the dissimilatory sulfate-reduction pathway

“…The consistent relative branching order of SRP taxa among the AprB and AprA trees indicates a shared evolutionary path for the aprB and aprA genes by vertical inheritance (speciation) and acquisition via concomitant LGT events, as demonstrated for the dissimilatory sulfite reductaseencoding genes dsrA and dsrB (Klein et al, 2001;Molitor et al, 1998;Zverlov et al, 2005). The topology of the AprB/ A-based trees of this study is congruent with the topology of an AprA-based tree of an earlier work (Friedrich, 2002).…”

“…The concurrent presence of apr and qmo genes in Chlorobiaceae and SRP genomes would have been the result of a subsequent, concerted LGT from an ancestral green sulfur bacterial donor to the sulfite-respiring ancestors of the SRP lineages. The second, alternative scenario implies an early divergence of the progenotic detoxifying AprBA into the phylogenetic lineages of the SOB and the SRP analogous to the postulated evolutionary path of DsrAB (Boucher et al, 2003;Molitor et al, 1998). The Qmo complex would then have originated within an ancestral sulfite-reducing bacterial lineage and not in an ancestor of the green sulfur bacteria, whereas AprM developed in ancestral purple sulfur bacteria.…”

“…Homologous proteins are also present in the anoxygenic photolithotrophic and chemolithotrophic sulfur-oxidizing bacteria (SOB) (Dahl & Trüper, 1994;Hipp et al, 1997;Schedel & Trüper, 1979, 1980Sperling et al, 1998;Trüper & Fischer, 1982). Indeed, earlier studies have confirmed that the dissimilatory APS reductases are highly conserved among SRP and SOB and form heterodimers with one alpha subunit (75-80 kDa, one FAD) and one beta subunit (18)(19)(20)(21)(22)(23) centres) which are encoded by the aprBA gene loci (Fritz et al, 2000;Hipp et al, 1997;Lampreia et al, 1994;Molitor et al, 1998;Speich et al, 1994). In contrast, the proteins that mediate the electron transport between the cytoplasmic AprBA and DsrAB and the quinol/quinone pool in the membrane are still poorly characterized.…”

The Crystal Structure of Desulfovibrio vulgaris Dissimilatory Sulfite Reductase Bound to DsrC Provides Novel Insights into the Mechanism of Sulfate Respiration

“…The dSiR is minimally composed of two subunits, DsrA and DsrB, in an ϳ200-kDa ␣ 2 ␤ 2 arrangement. The dsrA and dsrB genes are paralogous and most likely arose from a very early gene duplication event that preceded the separation of the archaea and bacteria domains (5)(6)(7)(8), in agreement with a very early onset of biological sulfite reduction. The dSiR belongs to a family of proteins that also include the assimilatory sulfite (aSiR) and nitrite (aNiR) reductases, the monomeric low molecular mass aSiRs, and other dSiRs like asrC and Fsr (9 -11).…”

“…The aSiR and aNiR, found in plants, fungi, and bacteria, are monomeric enzymes that display an internal two-fold symmetry of a module that is related to DsrA/DsrB, suggesting that these assimilatory proteins also resulted from a gene duplication event (9,10,14). Phylogenetic sequence analysis indicates that both dSiRs and aSiRs diverged from a common ancestral gene that was present in one of the earliest life forms on earth (7,10,14).Despite its central role in anaerobic metabolism, many aspects of dSiRs remain poorly understood. One of these is the …”