title: Domain evolution and functional diversification of sulfite reductases.
abstract: Sulfite reductases are key enzymes of assimilatory and dissimilatory sulfur metabolism, which occur in diverse bacterial and archaeal lineages. They share a highly conserved domain "C-X5-C-n-C-X3-C" for binding siroheme and iron-sulfur clusters that facilitate electron transfer to the substrate. For each sulfite reductase cluster, the siroheme-binding domain is positioned slightly differently at the N-terminus of dsrA and dsrB, while in the assimilatory proteins the siroheme domain is located at the C-terminus. Our sequence and phylogenetic analysis of the siroheme-binding domain shows that sulfite reductase sequences diverged from a common ancestor into four separate clusters (aSir, alSir, dsr, and asrC) that are biochemically distinct; each serves a different assimilatory or dissimilatory role in sulfur metabolism. The phylogenetic distribution and functional grouping in sulfite reductase clusters (dsrA and dsrB vs. aSiR, asrC, and alSir) suggest that their functional diversification during evolution may have preceded the bacterial/archaeal divergence.
authors.affiliation: Marine Biological Laboratory, The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Woods Hole, Massachusetts 02543, USA.
authors.forename: Ashita
authors.initials: A
authors.lastname: Dhillon
authors.forename: Sulip
authors.initials: S
authors.lastname: Goswami
authors.forename: Monica
authors.initials: M
authors.lastname: Riley
authors.forename: Andreas
authors.initials: A
authors.lastname: Teske
authors.forename: Mitchell
authors.initials: M
authors.lastname: Sogin
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000201:enzymology / Q000235:genetics; D001419:Bacteria / Q000201:enzymology / Q000235:genetics; D020134:Catalytic Domain / Q000235:genetics; D019143:Evolution, Molecular; D018559:Exobiology; D008969:Molecular Sequence Data; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D050862:Oxidoreductases Acting on Sulfur Group Donors