(A) Initial alignment of all disk rim connectors. The isosurface representation of the average is shown in the upper panel, the cross-section through the center in the lower panel. DM denotes disk membranes, DL the disk lumen, Cy the cytosol and DR the disk rim. The orange box marks the outline of the mask used for classification, the blue box the field of view in (B) and (C). (B) Three examples for class averages. A promising class which appears as a straight connector is boxed in green, an ambiguous class in yellow and a false-positives class in red. (C) Subvolume alignment of the promising class labelled with ‘1’ in (B). The left panel shows a cross section through the center of the average, middle and right panels are isosurface representations from two orientations. They display a clear connector between neighboring disk rims, but no further structural information can be inferred. (D–F) Similar analysis for disk interior connectors. (D) shows the initial alignment of all connectors, (E) three examples for class averages and (F) the alignment of the promising class labelled with ‘2’ in (E). M1 indicates the membrane at which the subvolume was extracted, M2 the second membrane within the same disk and M3 the neighboring disk.