Figure 1

(a) Side view (right) and cross section (top) of a new centriole assembling near-orthogonal to an existing one. Both the cartwheel (in blue) and the microtubules (in gray) have a ninefold symmetry that is thought to be imparted in large part by the self-assembly of SAS-6 proteins (left). The binding affinities for homodimerization through the coiled-coil domains and for oligomerization through the N-term domains have been measured in vitro to have the values shown. (b) Experimentally estimated concentrations of HsSAS-6 in the cytoplasm and at the centrosome of human cells.