a, Schematic of C. elegans separase and b, human separase structures. Human separase comprises an α-helical domain N-terminal to the common TPR domain not present in C. elegans separase. Auto-cleavage and phosphorylation sites in human separase are indicated. c, Structure-based alignment of the TPR domains of C. elegans and human separase. α-helices and corresponding TPR motifs, and Insert-1 and Insert-2 are shown. Human auto-cleavage sites from29,30. Phosphorylation sites from17,28. Sequence alignment figure generated using ALSCRIPT61. The species abbreviations are: Ce (Caenorhabditis elegans), Hs (Homo sapiens).