Yeast homologue of neuronal frequenin is a regulator of phosphatidylinositol-4-OH kinase

In metazoans, certain calmodulin-related calcium-binding proteins (recoveri ns, neurocalcins and frequenins) are found at highest levels in excitable c ells, but their physiological roles are largely uncharacterized. Here we sh ow that Saccharomyces cerevisiae contains a frequenin homologue, Frq1, and that its target is Pik1, a phosphatidylinositol-4-OH kinase. Frq1 binds to a conserved sequence motif in Pik1 outside Pik1's catalytic domain and stim ulates its activity in vitro. N-myristoylated Frq1 may also assist in Pik1 localization.