The crystal structure of apo-Pex5p(C). A. Structure of apo-Pex5p(C) elucidated from the novel crystal form. The bar at the bottom indicates the colour progression from N- to C-terminus. The N-terminal coiled segment is indicated with an "N", the TPR motifs are numbered 1–7 and the C-terminal 3-helix bundle is labelled "C". The position of the FEEEN motif is indicated by a red bar; the strontium ion with a red circle. The cylinder model above also highlights the FEEEN motif and strontium ion in red; the "*" indicates the PTS1-binding groove. B. Superposition of the new (blue) and old (cyan) apo-Pex5p(C) crystal structures. The C-terminal halves were superposed, to visualise the relative difference in the orientations between the N- and C-terminal halves. The Sr2+ ion is indicated in green, and it is clear that the hinge region for the observed movement lies in close vicinity to the Sr2+-binding site.