Fig. 2: Prohibitins form bell-shaped complexes at the MIM.
a, Cryo-tomograms of U2OS cells reveal bell-shaped assemblies at the inner membrane showing (i) a central tomographic slice of a tomogram showing multiple convex structures at the MIM (white arrowheads); (ii) a central tomographic slice at higher magnification (the convex structures feature a hollow core (side view); the lumen of the cristae is indicated with white asterisks); and (iii) a central tomographic slice at higher magnification. The structure appears as a ring (top view). b, Bell-shaped structures are a frequent feature of mammalian mitochondria, with (i) a central slice of an axonal mitochondrion of a rat hippocampal neuron and (ii) a central slice of a mitochondrion of a COS-7 cell. c, Quantification of convex complexes upon downregulation of PHB1 and PHB2. The boxes represent median, 25th and 75th percentiles, whiskers represent 10th and 90th percentiles. Three independent cultures for each condition were analysed (n = 3 independent experiments). Statistical comparisons using a two-sided Student’s t-test. P = 5 × 10−7 and P = 3.1 × 10−8. d, Rendering of the prohibitin subtomogram average (U2OS cells, 2.5 Å pixel size) results in a round bell-shaped assembly, with (i) the side view, (ii) the top view indicating 11 units making up the bell-shaped prohibitin complex and (iii) a clipping of the side view average. The dashed grey lines indicate the location of the MIM. Scale bars, 200 nm (in a (i) and b), 25 nm (in a (ii and iii)) and 10 nm (in d).
