A paradigm for biological sulfur transfers via persulfide groups: a persulfide-disulfide-thiol cycle in 4-thiouridine biosynthesis.

In support of the key features of sulfur transfer in the proposed mechanisms of 4-thiouridine generation, the enzyme ThiI can turn over only once in the absence of reductants of disulfide bonds, and Cys-456 of ThiI receives the sulfur transferred from the persulfide group of the sulfurtransferase IscS.