Mod5 catalyzes the transfer the delta2-isopropyl group from dimethylallyl diphosphate - a mevalonic acid derivative – to the exocyclic N6 of A36A37-containing tRNA (i6A37 formation). A single C2H2 Zn-finger-like motif present in this protein isabsent in the bacterial homolog. From a single gene MOD5, two mod5 isozymes (I, and II) are generated at the translation level (alternative translation initiation). Mod5-I is mainly located in mitochondria as well as in the cytoplasm, while Mod5-II is mainly located in the cytoplasm and in the nucleus, never in mitochondria. Sequence responsible for the subcellular distribution of the isozymes appears to reside in ‘accessory’ motifs missing from the prokaryotic counterpart (MiaA). Eukaryotic Mod5 is the ortholog of bacterial MiaA. There are no MiaA/Mod5 homologs in Archaea.