Sulphite efflux pump required for the secretion of sulphite as a reducing agent. In the presence of sulphite, cystine in keratin is directly cleaved to cysteine and S-sulphocysteine, and thereby, reduced proteins become accessible to hydrolysis by a variety of secreted endo- and exoproteases. Excretion of sulphite mediated by an efflux pump represents also an detoxification pathway for dermatophytes during infection of the epidermal stratum corneum, hair and nails, which are rich in cysteine (By similarity). Belongs to the tellurite-resistance/dicarboxylate transporter (TDT) family.