sequence of eIF4A-I IF4A1_MOUSE ATP-dependent RNA helicase eIF4A-1 Ddx2a EC 3.6.4.13 Eif4 Eif4a Eif4a1 Eukaryotic initiation factor 4A-I IMR:0703038 UniProt:P60843 eIF-4A-I eIF4A-I eukaryotic translation initiation factor 4A1 initiation factor eIF-4A long form molecule_role