Structural domains comprising this superfamily share the structure of the N-terminal domain of the highly conserved centriolar protein SAS-6 (spindle assembly abnormal protein 6). SAS-6 is the center of the cartwheel assembly that scaffolds centrioles early in their biogenesis. Structural studies have shown that SAS-6 self-associates in vitro into assemblies that resemble cartwheel centers through the formation of a parallel coiled-coil dimer PMID:21273447 This homodimers interact via virtue of their N-terminal domains to form oligomers. This oligomerization process is essential for centriole formation in C. elegans and human cells PMID:21273447.