Family member Swiss:P45573 has been observed to co-purify with Desulfovibrio vulgaris dissimilatory sulfite reductase [1], and many members of this family are annotated as the third (gamma) subunit of dissimilatory sulphite reductase. However, this protein appears to be only loosely associated to the sulfite reductase, which suggests that DsrC may not be an integral part of the dissimilatory sulphite reductase. Members of this family are found in organisms such as E. coli and H. influenzae which do not contain dissimilatory sulphite reductases but can synthesise assimilatory sirohaem sulphite and nitrite reductases. It is speculated that DsrC may be involved in the assembly, folding or stabilisation of sirohaem proteins [2]. The strictly conserved cysteine in the C terminus suggests that DsrC may have a catalytic function in the metabolism of sulphur compounds [3].

1: The third subunit of desulfoviridin-type dissimilatory sulfite reductases. Pierik AJ, Duyvis MG, van Helvoort JM, Wolbert RB, Hagen WR; Eur J Biochem 1992;205:111-115. PMID:1555572

2: A dissimilatory sirohaem-sulfite-reductase-type protein from the hyperthermophilic archaeon Pyrobaculum islandicum. Molitor M, Dahl C, Molitor I, Schafer U, Speich N, Huber R, Deutzmann R, Truper HG; Microbiology 1998;144:529-541. PMID:9493389

3: Sirohaem sulfite reductase and other proteins encoded by genes at the dsr locus of Chromatium vinosum are involved in the oxidation of intracellular sulfur. Pott AS, Dahl C; Microbiology 1998;144:1881-1894. PMID:9695921

4: Solution structure of Pyrobaculum aerophilum DsrC, an archaeal homologue of the gamma subunit of dissimilatory sulfite reductase. Cort JR, Mariappan SV, Kim CY, Park MS, Peat TS, Waldo GS, Terwilliger TC, Kennedy MA; Eur J Biochem 2001;268:5842-5850. PMID:11722571