Cloning and Characterization of the Polyether Salinomycin Biosynthesis Gene Cluster of Streptomyces albus XM211

Abstract

Salinomycin is widely used in animal husbandry as a food additive due to its antibacterial and anticoccidial activities. However, its biosynthesis had only been studied by feeding experiments with isotope-labeled precursors. A strategy with degenerate primers based on the polyether-specific epoxidase sequences was successfully developed to clone the salinomycin gene cluster. Using this strategy, a putative epoxidase gene, slnC, was cloned from the salinomycin producer Streptomyces albus XM211. The targeted replacement of slnC and subsequent trans-complementation proved its involvement in salinomycin biosynthesis. A 127-kb DNA region containing slnC was sequenced, including genes for polyketide assembly and release, oxidative cyclization, modification, export, and regulation. In order to gain insight into the salinomycin biosynthesis mechanism, 13 gene replacements and deletions were conducted. Including slnC, 7 genes were identified as essential for salinomycin biosynthesis and putatively responsible for polyketide chain release, oxidative cyclization, modification, and regulation. Moreover, 6 genes were found to be relevant to salinomycin biosynthesis and possibly involved in precursor supply, removal of aberrant extender units, and regulation. Sequence analysis and a series of gene replacements suggest a proposed pathway for the biosynthesis of salinomycin. The information presented here expands the understanding of polyether biosynthesis mechanisms and paves the way for targeted engineering of salinomycin activity and productivity.

High‐Performance Polymers from Nature: Catalytic Routes and Processes for Industry

“…We thought it possible that the deletion mutant Δ salE of S. albus might accumulate a metabolite bearing 1,2‐diol functionality at C19/C20, which would open up new possibilities for medicinal chemistry on this important molecule. This would fit the previous observation of a species with m / z 791.5 after deletion of this gene 7. We show here that strains in which salE is deleted from the salinomycin cluster actually produce two major components, E15 ( 2 ) and E16 ( 3 ), the structures of which confirm the predicted site‐specific alteration in salinomycin.…”

“…We6 and others7 have characterized the gene cluster that governs the biosynthetic pathway to salinomycin ( 1 ), a polyether ionophore antibiotic from Streptomyces albus that is used in animal husbandry to combat parasitic infections. Commercial fermentation of salinomycin is highly productive, reaching yields of up to 100 g L −1 .…”

HDAC inhibitors enhance the lethality of low dose salinomycin in parental and stem-like GBM cells

“…3 In 2009 Gupta et al, after screening a library of ~16 000 compounds, expanded the potential utility of salinomycin positing its use as an anti-cancer stem cell drug in breast cancer. 4,5 It was stated that salinomycin was 100× more potent at killing breast cancer stem cells than a standard of care agent such as paclitaxel.…”

Streptomycetes: Surrogate hosts for the genetic manipulation of biosynthetic gene clusters and production of natural products

“…S. coelicolor A3(2) has proven to be an efficient recipient host for giant clusters. Salinomycin, a polyether antibiotic used to prevent Coccidioidomycosis in poultry and to alter gut flora to improve nutrient absorption in ruminants, is generated by an assembly line of nine polyketide synthases (PKSs) (Jiang et al, 2012; Yin et al, 2015). Yin et al isolated three fragments of the salinomycin gene cluster from S. albus DSM 1398, assembled them into a single 106-kb DNA fragment using the Red/ET recombination technique, and successfully expressed the giant cluster in the wild-type S. coelicolor A3(2) and restored salinomycin production (Yin et al, 2015).…”