Figure 2: Three-dimensional arrangement of mitoribosomes in membrane-bound polyribosomes.
From: Organization of the mitochondrial translation machinery studied in situ by cryoelectron tomography
(a) For the analysis of the 3D distribution of mitoribosomes, two angles were defined: the angle α between the y axis of the mitoribosome under scrutiny and the centre-to-centre vector 
of another mitoribosome describes their relative positions, while the angle β between the vectors 
and 
of the two mitoribosomes captures their relative orientation. (b) The plot of α against β and subsequent clustering of the data set (730 pairwise mitoribosome arrangements) reveals two highly populated classes I and II that represent the left and right neighbour in the same 3D arrangement of mitoribosomes. (c) Preferred 3D arrangement of membrane-bound mitoribosomes, visualized by replicates of the template structure, looking down on the inner membrane. The shortest path between mRNA entry and exit sites of adjacent mitoribosomes was indicated (green) to visualize a possible pathway for polysomal mRNA. (d) Class I from b was further subdivided into three equally populated clusters (I–I to I–III) according to the relative position of adjacent mitoribosomes. (e) Schematic representation of the ribosomal arrangements represented by classes I–I to I–III and the modelled pathways of polysomal mRNA.
