Showdomycin, 5-Hydroxyuridine, and 5-Aminouridine

The antibiotic, showdomycin, has a structural similarity to n-ethylmaleimide, a thiol binding reagent, and also to the nucleosides, uridine and pseudouridine. Its reactivity toward sulfhydryl-groups of susceptible proteins results from its maleimide-like structure and accounts for its cytotoxic effects. However, its nucleoside like structure is also related to its function as evidenced by the capacity of nucleosides to reverse its inhibitory effects on growth and on the transport of sugars and amino acids in Escherichia coli. This interesting specificity, as well as the remarkable changes which occur in showdomycin-resistant mutants of E. coli, are the basis for continued interest in this antibiotic.