Iron-sulfur cluster-binding SPASM domain of butirosin biosynthesis protein N
Butirosin biosynthesis protein N (BtrN), also called S-adenosyl-L-methionine-dependent 2-deoxy-scyllo-inosamine dehydrogenase (EC 220.127.116.11), is a radical S-adenosylmethionine (SAM) enzyme that catalyzes the two-electron oxidation of 2-deoxy-scyllo-inosamine (DOIA) to amino-dideoxy-scyllo-inosose (amino-DOI) in the biosynthetic pathway of the aminoglycoside antibiotic butirosin. Radical SAM enzymes are characterized by a conserved CxxxCxxC motif, which coordinates the conserved iron-sulfur cluster that is involved in the reductive cleavage of SAM and generates a 5'-deoxyadenosyl radical, which in turn abstracts a hydrogen from the appropriately positioned carbon atom of the substrate. Radical SAM enzymes with a C-terminal SPASM domain contain at least one other iron-sulfur cluster. BtrN contains one auxillary 4Fe-4S cluster.