Functions in the biosynthesis of archaeosine, a modified nucleoside present in the dihydrouridine loop (D-loop) of archaeal tRNAs. Catalyzes the addition of L-lysine to the cyano group of 7-cyano-7-deazaguanine (preQ0)-modified tRNAs at position 15, to generate q0kN15-tRNA, a q0N lysine adduct identified as 7-N-[(5S)-5-amino-5-carboxypentyl]formamidino-7-deazaguanosine. 7-cyano-7-carbaguanosine(15) in tRNA + L-lysine = 7-N-[(5S)-5-amino-5-carboxypentyl]formamidino-7-deazaguanosine(15) in tRNA tRNA modification; archaeosine-tRNA biosynthesis. Forms a robust complex with the archaeosine synthase beta subunit RaSEA, likely an alpha(2)beta(2) heterotetrameric structure. Formation of this complex highly increases lysine transfer activity. Belongs to the archaeosine synthase type 1 family.