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. Archaeosine is no more detected among the modified nucleosides in tRNA fractions. Belongs to the archaeosine synthase type 1 family.