C-type monoheme cytochrome, which is part of the SoxAX cytochrome complex involved in sulfur oxidation. The SoxAX complex catalyzes the formation of a heterodisulfide bond between the conserved cysteine residue on a sulfur carrier SoxYZ complex subunit SoxY and thiosulfate or other inorganic sulfur substrates. This leads to the intermediary formation of conspicuous sulfur globules inside of the cells. 2 Fe(III)-[cytochrome c] + L-cysteinyl-[SoxY protein] + thiosulfate = 2 Fe(II)-[cytochrome c] + 2 H(+) + S-sulfosulfanyl-L-cysteinyl-[SoxY protein] 2 Fe(III)-[cytochrome c] + S-sulfanyl-L-cysteinyl-[SoxY protein] + thiosulfate = 2 Fe(II)-[cytochrome c] + 2 H(+) + S-(2-sulfodisulfanyl)-L-cysteinyl-[SoxY protein] Binds 1 heme group per subunit. Heterodimer of SoxA and SoxX. By thiosulfate. Cysteine persulfide at Cys-242. No oxidation of thiosulfate with a simultaneous deletion of soxX alone or together with a deletion of soxB. Belongs to the SoxA family.