Dentatorubral-pallidoluysian atrophy (DRPLA) is caused by expansion of a glutamine repeat in DRPLA protein. Rat DRPLA protein, homologous in sequence to human DRPLA protein, was identified in rat brains. Immunoblots of human control and rat brain tissues with and without reduction show that human DRPLA protein forms more disulfide-bond complexes than rat DRPLA protein. An immunohistochemical study and a subcellular fractionation experiment show that human DRPLA protein produces complexes within the cytoplasm of neurons, whereas rat DRPLA protein rarely does. In spite of the close homology of their amino acid sequences, human and rat DRPLA protein have different protein characters. The differences in these characters suggest structural differences and may be related to these proteins functions. (C) 1998 Academic Press.