(A) shows the overall structure of eIF3k from the PDB-entry 1RZ4  with β-strands and α-helices represented as ribbons and cylinders, respectively. Regions of the structure with sequence similarity to canonical PCI domain are rendered in colour. Regions belonging to the WH subdomain are shown in green, while conserved structure elements of the helical hairpin regions are shown in dark blue. The connection between β-strand 2 and 3 is not resolved and thus missing in 1RZ4. Other regions (extreme N- and C- termini, connecting helices between hairpins, unstructured regions) are shown in grey. (B) Model of a PCI protein with three additional helical hairpins upstream of the PCI domain. Within the PCI domains, only regions that can be modelled on the eIF3k template are shown. The N-terminal extension is shown in light blue, the other colours are as in figure 3a.