F420‐dependent sulfite reductase [siroheme], sulfite → sulfide. Catalyzes the reduction of sulfite to sulfide using reduced F420 as the electron source. Involved in sulfite detoxification and assimilation. Cannot use NADH or NADPH.
MYEWKLNEIVDSGVCARCGTCTIVCPNGILTFDERPKLIDECLRKGHGMCFEVCPRVSSA
KYQIKIREKFYEKYYYAKSDIEGQDGGVVTAFLKYLLENGKIDGAIVVGDECWKPVSLVV
QNAEDLLKTAKSKYAISTLDALRKAGEMGLEKVAVVGLPCQINGLRKLQYFPYHAKHDLE
LGRNGKPVKLPKIEYLIGLFCTEKFRYDNMKEVLSKHGIDIEKVEKFDIKKGKLLVYVNG
EKKEFDLKEFEICSGCKMCRDFDAEMADVSVGCVGSPDGYSTIIIRTEKGEEIKNAVELK
EGVNLEEIEKLRQLKLKRFKKEVERRRENNEYVSFYWTADYGGIGKRADGTYFIRVRAKP
GGWYKPEEIKEILDIAEEYNAKIKVTDRAGYELHGISGFDVEDIVLRLREKGLLTGSEGP
LVRATLACPGGGNCSSGLVDTTELARIIEDNFKERPAPYKFKIAISGCPNGCVRPQVHDI
GIAGVKYPKVNEEKCNGCGRCAEVCKVEAIDIRGETSYTNYNVCVGCGKCIKNCPNEARE
VKEEGYLVYVGGKTGREVVEGVKMKLMSVDEIINFIDKVLVVYGKYAEKPQRERLAAVMK
RVGYGKFLEEVKELMKKEIC630
| PMID | Title & Author | Abstract | Year | |
| 0 | 16048999 | A new type of sulfite reductase, a novel coenzyme F420-dependent enzyme, from the methanarchaeon Methanocaldococcus jannaschii.Johnson E.F., Mukhopadhyay B. | Methanocaldococcus jannaschii is a hypertheromphilic, strictly hydrogenotrophic, methanogenic archaeon of ancient lineage isolated from a deep-sea hydrothermal vent. It requires sulfide for growth. Sulfite is inhibitory to the methanogens. Yet, we observed that M. jannaschii grows and produces methane with sulfite as the sole sulfur source. We found that in this organism sulfite induces a novel, highly active, coenzyme F(420)-dependent sulfite reductase (Fsr) with a cell extract specific activity of 0.57 mumol sulfite reduced min(-1) mg(-1) protein. The cellular level of Fsr protein is comparable to that of methyl-coenzyme M reductase, an enzyme essential for methanogenesis and a possible target for sulfite. Purified Fsr reduces sulfite to sulfide using reduced F(420) (H(2)F(420)) as the electron source (K(m): sulfite, 12 microm; H(2)F(420), 21 microm). Therefore, Fsr provides M. jannaschii an anabolic ability and protection from sulfite toxicity. The N-terminal half of the 70-kDa Fsr polypeptide represents a H(2)F(420) dehydrogenase and the C-terminal half a dissimilatory-type siroheme sulfite reductase, and Fsr catalyzes the corresponding partial reactions. Previously described sulfite reductases use nicotinamides and cytochromes as electron carriers. Therefore, this is the first report of a coenzyme F(420)-dependent sulfite reductase. Fsr homologs were found only in Methanopyrus kandleri and Methanothermobacter thermautotrophicus, two strictly hydrogenotrophic thermophilic methanogens. fsr is the likely ancestor of H(2)F(420) dehydrogenases, which serve as electron input units for membrane-based energy transduction systems of certain late evolving archaea, and dissimilatory sulfite reductases of bacteria and archaea. fsr could also have arisen from lateral gene transfer and gene fusion events. | 2005 |
| 1 | 18378657 | Coenzyme F420-dependent sulfite reductase-enabled sulfite detoxification and use of sulfite as a sole sulfur source by Methanococcus maripaludis.Johnson E.F., Mukhopadhyay B. | Coenzyme F(420)-dependent sulfite reductase (Fsr) of Methanocaldococcus jannaschii, a sulfite-tolerant methanogen, was expressed with activity in Methanococcus maripaludis, a sulfite-sensitive methanogen. The recombinant organism reduced sulfite to sulfide and grew with sulfite as the sole sulfur source, indicating that Fsr is a sulfite detoxification and assimilation enzyme for methanogens and that M. maripaludis synthesizes siroheme. | 2008 |
| 2 | 30559729 | Comparative Genomics and Proteomic Analysis of Assimilatory Sulfate Reduction Pathways in Anaerobic Methanotrophic Archaea | Sulfate is the predominant electron acceptor for anaerobic oxidation of methane (AOM) in marine sediments. This process is carried out by a syntrophic consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria (SRB) through an energy conservation mechanism that is still poorly understood. It was previously hypothesized that ANME alone could couple methane oxidation to dissimilatory sulfate reduction, but a genetic and biochemical basis for this proposal has not been identified. Using comparative genomic and phylogenetic analyses, we found the genetic capacity in ANME and related methanogenic archaea for sulfate reduction, including sulfate adenylyltransferase, APS kinase, APS/PAPS reductase and two different sulfite reductases. Based on characterized homologs and the lack of associated energy conserving complexes, the sulfate reduction pathways in ANME are likely used for assimilation but not dissimilation of sulfate. Environmental metaproteomic analysis confirmed the expression of 6 proteins in the sulfate assimilation pathway of ANME. The highest expressed proteins related to sulfate assimilation were two sulfite reductases, namely assimilatory-type low-molecular-weight sulfite reductase (alSir) and a divergent group of coenzyme F420-dependent sulfite reductase (Group II Fsr). In methane seep sediment microcosm experiments, however, sulfite and zero-valent sulfur amendments were inhibitory to ANME-2a/2c while growth in their syntrophic SRB partner was not observed. Combined with our genomic and metaproteomic results, the passage of sulfur species by ANME as metabolic intermediates for their SRB partners is unlikely. Instead, our findings point to a possible niche for ANME to assimilate inorganic sulfur compounds more oxidized than sulfide in anoxic marine environments. | 2018 |
Johnson, E.F., and Mukhopadhyay, B. (2005) A new type of sulfite reductase, a novel coenzyme F420‐dependent enzyme, from the methanarchaeon Methanocaldococcus jannaschii. J Biol Chem 280: 38776–38786.