Novel mechanism of hydrogen peroxide for promoting efficient natamycin synthesis in .

The mechanism of regulation of natamycin biosynthesis by Streptomyces in response to oxidative stress is unclear. Here, we first show cholesterol oxidase SgnE, which catalyzes the formation of HO from sterols, triggered a series of redox-dependent interactions to stimulate natamycin production in . In response to reactive oxygen species, residues Cys212 and Cys221 of the HO-sensing consensus sequence of OxyR were oxidized, resulting in conformational changes in the protein: OxyR extended its DNA-binding domain to interact with four motifs of promoter p . This acted as a redox-dependent switch to turn on/off gene transcription of , which encodes a cluster-situated regulator, by controlling the affinity between OxyR and p , thus regulating the expression of 12 genes in the natamycin biosynthesis gene cluster. OxyR cooperates with SgnR, another cluster-situated regulator and an upstream regulatory factor of SgnM, synergistically modulated natamycin biosynthesis by masking/unmasking the -35 region of p depending on the redox state of OxyR in response to the intracellular HO concentration. IMPORTANCE Cholesterol oxidase SgnE is an indispensable factor, with an unclear mechanism, for natamycin biosynthesis in . Oxidative stress has been attributed to the natamycin biosynthesis. Here, we show that SgnE catalyzes the formation of HO from sterols and triggers a series of redox-dependent interactions to stimulate natamycin production in . OxyR, which cooperates with SgnR, acted as a redox-dependent switch to turn on/off gene transcription of , which encodes a cluster-situated regulator, by masking/unmasking its -35 region, to control the natamycin biosynthesis gene cluster. This work provides a novel perspective on the crosstalk between intracellular ROS homeostasis and natamycin biosynthesis. Application of these findings will improve antibiotic yields via control of the intracellular redox pressure in .