Streptavidins play a multifunctional role within a biotin-pathway antibiotic network encoded in a biosynthetic supercluster

Streptavidin, the well-known biotin-binding protein extensively used in biotechnology, is naturally co-produced in Streptomyces avidinii alongside stravidins—inhibitors of biotin biosynthesis. Here, we uncover and activate a conserved genomic region flanked by two streptavidin genes, revealing multiple biosynthetic gene clusters that produce diverse biotin-related metabolites, including stravidins, acidomycin, α-methyl-KAPA, α-methyldesthiobiotin, and the novel non-proteinogenic amino acid ANDA. We show α-methyldesthiobiotin arises from α-methyl-KAPA, illustrating how methylated analogues interfere with distinct steps of biotin biosynthesis. Contrary to the view that streptavidin functions solely by sequestering biotin, our biochemical, structural, and bioactivity analyses demonstrate that it also binds acidomycin, neutralizing its antibacterial activity to protect the producer while likely facilitating compound secretion. The crystal structure of the streptavidin–acidomycin complex reveals the molecular basis for this dual functionality. Our findings establish a multifunctional streptavidin that integrates biotin sequestration and self-resistance to balance an antibiotic network targeting the biotin pathway in microbial competition.