Figure 3.

Cryo-ET reconstruction of circular polyribosomes. Nonasome (A) and undecasome (B) formed on uncapped non-adenylated GFP-encoding mRNA, 750-nt coding sequence (construct 2, see Materials and Methods). The ribosomes involved in 3D bulges (see the text) are inscribed into a dashed-line cycle. The undecasome (B) is an example of a double-row polyribosome with anti-parallel paths of the mRNA chain (collapsed circle). Here and in the following Figures 4–6, the left-hand panels present the vertical projections (elevation views) of the polyribosome reconstruction images. The middle panels show the side projections of the same polyribosome reconstruction. The right-hand panels present the deduced path of mRNA, the arrowheads being markers of the direction of mRNA path through the ribosomes. The asterisk indicates the presumed site of the junction of the 5′ and 3′ ends of mRNA, suggested by the gap and/or irregularity in orientation of neighboring ribosomes.