Sterol Sponge Mechanism Is Conserved for Glycosylated Polyene Macrolides

Amphotericin-like glycosylated polyene macrolides (GPMs) are a clinically and industrially important family of natural products, but the mechanisms by which they exert their extraordinary biological activities have remained unclear for more than half a century. Amphotericin B exerts fungicidal action primarily via self-assembly into an extramembranous sponge that rapidly extracts ergosterol from fungal membranes, but it has remained unclear whether this mechanism is applicable to other GPMs. Using a highly conserved polyene-hemiketal region of GPMs that we hypothesized to represent a conserved ergosterol-binding domain, we bioinformatically mapped the entirety of the GPM sequence-function space and expanded the number of GPM biosynthetic gene clusters (BGCs) by 10-fold. We further leveraged bioinformatic predictions and tetrazine-based reactivity screening targeting the electron-rich polyene region of GPMs to discover a first-in-class methyltetraene- and diepoxide-containing GPM, kineosporicin, and to assign BGCs to many new producers of previously reported members. Leveraging a range of structurally diverse known and newly discovered GPMs, we found that the sterol sponge mechanism of fungicidal action is conserved.