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Thermus thermophilus SoxB and related proteins, N-terminal metallophosphatase domain SoxB (sulfur oxidation protein B) is a periplasmic thiosulfohydrolase and an essential component of the sulfur oxidation pathway in archaea and bacteria. SoxB has a dinuclear manganese cluster and is thought to catalyze the release of sulfate from a protein-bound cysteine S-thiosulfonate. SoxB is expressed from the sox (sulfur oxidation) gene cluster, which encodes 15 other sox genes, and has two domains, an N-terminal metallophosphatase domain and a C-terminal 5'-nucleotidase domain. SoxB binds the SoxYZ complex and is thought to function as a sulfate-thiohydrolase. SoxB is closely related to the UshA, YchR, and CpdB proteins, all of which have the same two-domain architecture. The N-terminal metallophosphatase domain belongs to a large superfamily of distantly related metallophosphatases (MPPs) that includes: Mre11/SbcD-like exonucleases, Dbr1-like RNA lariat debranching enzymes, YfcE-like phosphodiesterases, purple acid phosphatases (PAPs), YbbF-like UDP-2,3-diacylglucosamine hydrolases, and acid sphingomyelinases (ASMases). MPPs are functionally diverse, but all share a conserved domain with an active site consisting of two metal ions (usually manganese, iron, or zinc) coordinated with octahedral geometry by a cage of histidine, aspartate, and asparagine residues. The conserved domain is a double beta-sheet sandwich with a di-metal active site made up of residues located at the C-terminal side of the sheets. This domain is thought to allow for productive metal coordination. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",