Brefeldin A binds to glutathione S-transferase and is secreted as glutathione and cysteine conjugates by Chinese hamster ovary cells.

Radioactively labeled brefeldin A was used to probe for proteins that interact with this metabolite. The most prominent protein labeled after in vivo incubation of Chinese hamster ovary cells with [3H]brefeldin A turned out to have an apparent molecular mass of 26 kDa. Radioactive peptides derived from the [3H]brefeldin A-labeled protein showed sequence identity with glutathione S-transferases, and immunoblotting after two-dimensional gel electrophoresis confirmed this result. In addition, Chinese hamster ovary cells convert the antibiotic to its glutathionyl and cysteinyl derivatives and secrete them rapidly into the medium. From these findings we conclude that detoxification of the antibiotic in mammalian cells occurs via the glutathion S-transferase system. This may explain the often observed reversibility of brefeldin A's action on the steady state of organelles in mammalian cells.