The biosynthetic gene cluster of the C-nucleoside antibiotic pyrazomycin with a rare pyrazole moiety
Pyrazomycin is a rare C-nucleoside antibiotic with a naturally occurring pyrazole ring, whose biosynthetic origin has remained obscure for decades. In this study, we report the identification of the gene cluster responsible for pyrazomycin biosynthesis in Streptomyces candidus NRRL 3601, revealing that StrR-family regulator PyrR is the cluster-situated transcriptional activator governing pyrazomycin biosynthesis. Furthermore, our results from in vivo reconstitution and stable-isotope feeding experiments support that PyrN is a new nitrogen-nitrogen bond forming enzyme linking the {varepsilon}-NH2 nitrogen of O_SCPLOWLC_SCPLOW-N6-OH-lysine and -NH2 nitrogen of O_SCPLOWLC_SCPLOW-glutamate. This study lays the foundation for further genetic and biochemical characterization of pyrazomycin pathway enzymes constructing the characteristic pyrazole ring.