Identification of a human centrosomal calmodulin-binding protein that shares homology with pericentrin

Eukaryotic chromosome segregation depends on the mitotic spindle apparatus, a bipolar array of microtubules nucleated from centrosomes. Centrosomal mi crotubule nucleation requires attachment of gamma-tubulin ring complexes to a salt-insoluble centrosomal core, but the factor(s) underlying this attac hment remains unknown. In budding yeast, this attachment is provided by the coiled-coil protein Spc110p, which links the yeast gamma-tubulin complex t o the core of the yeast centrosome. Here, we show that the large coiled-coi l protein kendrin is a human orthologue of Spc110p. We identified kendrin b y its C-terminal calmodulin-binding site, which shares homology with the Sp c110p calmodulin-binding site. Kendrin localizes specifically to centrosome s throughout the cell cycle. N-terminal regions of kendrin share significan t sequence homology with pericentrin, a previously identified murine centro some component known to interact with gamma-tubulin. In mitotic human breas t carcinoma cells containing abundant centrosome-like structures, kendrin i s found only at centrosomes associated with spindle microtubules.