An FAD-dependent pyridine nucleotide-disulfide oxidoreductase is involved in disulfide bond formation in FK228 anticancer depsipeptide.

Disulfide bonds are rare in bacterial natural products, and the mechanism of disulfide bond formation in those products is unknown. Here we characterize a gene and its product critical for a disulfide bond formation in FK228 anticancer depsipeptide in Chromobacterium violaceum. Deletion of depH drastically reduced FK228 production, whereas complementation of the depH-deletion mutant with a copy of depH on a medium copy-number plasmid not only fully restored the FK228 production but also significantly increased the FK228 yield. Purified 6xHis-tagged DepH fusion protein in native form is a homodimer of 71.0 kDa, with each monomer containing one molecule of FAD. DepH efficiently converts an immediate FK228 precursor to FK228 in the presence of NADP(+). We conclude that DepH is an FAD-dependent pyridine nucleotide-disulfide oxidoreductase, specifically and efficiently catalyzing a disulfide bond formation in FK228.