Structure and interactions of the translation initiation factor eIF1

eIF1 is a universally conserved translation factor that is necessary for sc anning and involved in initiation site selection. We have determined the so lution structure of human eIF1 with an N-terminal His tag using NMR spectro scopy. Residues 29-113 of the native sequence form a tightly packed domain with two alpha-helices on one side of a five-stranded parallel and antipara llel beta-sheet, The fold is new but similar to that of several ribosomal p roteins and RNA-binding domains. A likely binding site is indicated by yeas t mutations and conserved residues located together on the surface. No inte raction with recombinant eIF5 or the initiation site RNA GCCACAAUGGCA was d etected by NMR, but GST pull-down experiments show that eIF1 binds specific ally to the p110 subunit of eIF3, This interaction explains how eIF1 is rec ruited to the 40S ribosomal subunit.