Characterization of self-assembly of Euplotes octocarinatus centrin

Centrin, an EF-hand calcium-binding protein with high homology to calmodulin (CaM), is an essential component for microtubule-organizing center (MTOC) in organisms ranging from algae and yeast to human. It plays an important structural role by contributing to the formation of Ca(2+)-sensitive contractile filaments and some super-molecular assemblies. Previous work suggests that the N-terminal domain of centrin especially its first 20-residue fragment, is required for the self-assembly of protein. Native polyacrylamide gel electrophoresis (native-PAGE), pull-down assay, fluorescence resonance light scattering (RLS) and yeast two-hybrid assay indicate that the C-terminal domain of Euplotes octocarinatus centrin (EoCen) also contributes to the centrin self-assembly besides its N-terminal domain in vivo and in vitro. On the basis of our results, a self-assembly mode of centrin, which is C-to-C as well as N-to-N (between C- and C-terminal domains as well as between N- and N-terminal domains), is put forward providing maybe some insights into the molecular mechanism of centrin functions in the cell.