(A) Two views of C. elegans HIM-3, with HORMA domain colored as a rainbow from N- to C-termini and secondary structure elements labeled according to the Mad2 convention (Luo et al., 2002; Sironi et al., 2002), with the C-terminal “closure motif” residues 278-285 in gray (see schematic, top). See Figure S1A for comparison with Mad2 and Rev7. (B) Detail view showing interactions between the closure motif and the “safety belt” of HIM-3. (C) Left: schematic of HIM-3, HTP-1, HTP-2 and HTP-3 N-terminal HORMA domains and C-terminal “closure motifs.” Right: alignment of putative closure motifs from all four C. elegans HORMA domain proteins. See also Figure S1B-D.