    1.8.99.5 | structure with the alpha and beta subunits bound to the DsrC protein. The alpha2beta2gamma2 assembly contains two siroheme-[4Fe4S] cofactors bound by DsrB, two sirohydrochlorins and two [4Fe-4S]-centers bound by DsrA, and another four [4Fe-4S]-centers in the ferredoxin domains. A sulfite molecule, coordinating the siroheme, is found at the active site. The DsrC protein is bound in a cleft between DsrA and DsrB with its conserved C-terminal cysteine reaching the distal side of the siroheme. The process of sulfite reduction may involve DsrAB, DsrC, and the DsrMKJOP membrane complex (a membrane complex with putative disulfide/thiol reductase activity), in which two of the six electrons for reduction of sulfite derive from the membrane quinone pool |
