Radical SAM enzyme involved in the synthesis of archaeosine, a modified nucleoside present in the dihydrouridine loop (D-loop) of archaeal tRNAs. Catalyzes the cleavage of the C(epsilon)-N bond of the lysine moiety of q0kN15-tRNA, leading to the formation of archaeosine at position 15 in tRNAs. 7-N-[(5S)-5-amino-5-carboxypentyl]formamidino-7-deazaguanosine(15) in tRNA + S-adenosyl-L-methionine = 5'-deoxyadenosine + archaeosine(15) in tRNA + 2 H(+) + L-1-piperideine-6-carboxylate + L-methionine Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. tRNA modification; archaeosine-tRNA biosynthesis. Forms a robust complex with the archaeosine synthase alpha subunit ArcS (PubMed:31740832). This complex likely consists of an alpha(2)beta(2) heterotetrameric structure (By similarity). Belongs to the radical SAM superfamily. RaSEA family. Extended N-terminus.