3D subtomogram average of a cytoplasmic ribosome optimally positioned for protein import on the OMM shows multiple contact points. (A) Three views of the subtomogram average of a cytoplasmic ribosome positioned with the exit tunnel on the 60S subunit (dark blue) facing the OMM (gray). Three connecting densities (labeled 1, 2, 3 in pink, orange, and green, respectively) are visible between the 60S and the OMM surrounding the peptide exit tunnel (dashed circle). (B) The subtomogram average of the mitochondria-associated ribosome (blue transparent density) with a fitted atomic model of the S. cerevisiae 80S ribosome (PDB 4V6I). Boxed regions focus on the cryo-EM density of each of the three connections observed between the cytoplasmic ribosome and the OMM.