Abstract
Uptake of thiosulfate ions as an inorganic sulfur source from the environment is important for bacterial sulfur assimilation. Recently, a selective thiosulfate uptake pathway involving membrane protein YeeE (TsuA) was characterized. However, the precise function of YeeE and a putative cofactor in the thiosulfate ion uptake pathway remained unclear. Here, we assessed selective thiosulfate transport via YeeE in vitro and characterized YeeD (TsuB) as an adjacent and essential cofactor for YeeE-mediated thiosulfate uptake in vivo. We further showed that YeeD possesses thiosulfate decomposition activity and that a conserved cysteine in YeeD was modified in several forms in the presence of thiosulfate. Finally, the crystal structure of a YeeE-YeeD fusion protein at 2.6-Å resolution revealed their interactions. The association was evaluated by a binding assay using purified proteins. Based on these results, a model of the sophisticated uptake of thiosulfate ions by YeeE and YeeD is proposed.
Competing Interest Statement
The authors have declared no competing interest.
