Nikkomycins and polyoxins are antifungal peptidylnucleoside antibiotics active against human and plant pathogens. During peptidylnucleoside biosynthesis in Streptomyces cacaoi and S. tendae, the C5′ extension of the nucleoside, essential for downstream structural diversification, is catalyzed by a conserved radical S-adenosyl-L-methionine (SAM) enzyme, PolH or NikJ. This is distinct from the nucleophilic mechanism reported for antibacterial nucleosides and represents a new mechanism of nucleoside natural product biosynthesis. Read more