Fig. 4. Peripheral subunits of eIF3.

a, Segmented cryo-EM reconstruction focused on eIF3 peripheral subunits localized near the mRNA channel entry, below DHX29, seen from the solvent face (left) and from below (middle). Close-up view of eIF3 peripheral subunits seen from below (right), with a red arrowhead indicating the connection with ES6^S-hA and numbers indicating the blades of the β-propeller structure. b Atomic model of rabbit eIF3b (orange), yeast eIF3i (purple) and a long α-helix (red) corresponding to a fragment of the C-terminal helical region (‘eIF3a C-ter’). c, Left, front view of eIF3b and eIF3i subunits bound to the 40S subunit and DHX29 in the context of the 43S complex. The remaining, unmodeled third of DHX29 is denoted as a transparent green surface, based on its cryo-EM density. Right, close-up view of the contact points between eIF3b and DHX29. The panel also shows eIF3i's interaction with DHX29. d, Left, segmented cryo-EM reconstruction focused on an eIF3 peripheral subunit tentatively identified as eIF3d, localized on the 40S head behind ribosomal protein RACK1. Middle, the same reconstruction seen from above, rendered in transparent with the atomic model of the human 40S subunit fitted in. Right, close-up view of the putative eIF3d subunit. Red arrow indicates a density bridging the globular domain of eIF3d to a density corresponding to the eIF2α-D1 domain, part of the eIF2-TC (density colored in gold). Colored arrowheads indicate the interaction of eIF3 peripheral subunits with various ribosomal proteins.