A novel human gene (sazD) that maps to the autosomal dominant polycystic kidney disease region shares sequence similarity with members of the beta-transducin superfamily. The cDNA sazD-c predicts an approximately 58-kDa protein (sazD) with seven internal repeats, similar to the WD-40 motif of the transducin family. The size of this protein family has been expanding rapidly; however, neither the structure nor the function of this repeated motif is known. Preliminary data do not suggest that sazD is mutated in patients with polycystic kidney disease.