Requires Mg2+. The enzyme is a member of the superfamily of?S-adenosyl-L-methionine-dependent radical (radical AdoMet) enzymes. Binds a [4Fe-4S] cluster that is coordinated by 3 cysteines and an exchangeable?S-adenosyl-L-methionine molecule. The?S-adenosyl-L-methionine is catalytic as it is regenerated at the end of the reaction. The reaction is part of the biosynthesis pathway of queuosine.