Isolation of a complementary DNA clone encoding an autoantigen recognized by an anti-neuronal cell antibody from a patient with paraneoplastic cerebellar degeneration. We isolated a complementary DNA clone encoding a 52-kd protein recognized by an anti-neuronal cell antibody in serum from a patient with paraneoplastic cerebellar degeneration associated with uterine carcinoma. The recombinant protein expressed in prokaryotic cells was specifically recognized by the anti-neuronal cell antibody from the patient, and its molecular weight was identical to that of antigenic proteins in the cerebellum. The deduced protein consisted of 450 amino acids dominated by hydrophilic residues, the calculated relative molecular mass was 51,238, and the predicted value of the isoelectric point was 4.99. This complementary DNA sequence and the deduced protein sequence have not been reported previously, and the sequences showed no homologies with the complimentary DNA or the amino acid sequences in the GenBank, EMBL, or NBRF databases, including the complementary DNA for a 34-kd cerebellar protein (CDR34) that is recognized by an anti-Purkinje cell antibody. Unexpectedly, the transcript of this gene was detected not only in the cerebellum and the brain stem but also in an extraneural tissue, the intestine. 