CA projections C1a, e, and c are lost in the pf16 mutant, and the PF16 C-terminus locates to the C1a projection. (A – P) Tomographic slices (columns 1 and 2) and isosurface renderings (columns 3 and 4) of the averaged CA repeats of WT (A–D), 9+2 pf16 (E and F), and the tagged rescue pf16;PF16::BCCP without adding nanogold (I–L, control) and after treatment with streptavidin gold (M–P) in cross-sectional (columns 1 and 3) and longitudinal views (columns 2 and 4). The thin blue line in A indicates the location of the slices shown in column 2. The C1a, e, and c projections (indicated by black brackets in A and C) were missing in the pf16 mutant (white bracket in E). When the C-terminus of PF16 was tagged with BCCP, the additional density of the BCCP-streptavidin-gold label was detected in the C1a projection (blue arrowheads in M–P); this label density was not observed in WT (white arrowheads in A–D) or control samples (white arrowheads in I–L). Scale bar in N, 20 nm (valid for all EM images).