2 DROSOPHILA NERVOUS-SYSTEM ANTIGENS, NERVANA-1 AND NERVANA-2, ARE HOMOLOGOUS TO THE BETA-SUBUNIT OF NA-ATPASE(,K+)

A nervous system-specific glycoprotein antigen from adult Drosophila h eads, designated Nervana (Nrv), has been purified on the basis of reac tivity of its carbohydrate epitope(s) with anti-horseradish peroxidase (HRP) antibodies that are specific markers for Drosophila neurons, An ti-Nrv monoclonal antibodies (mAbs), specific for the protein moiety o f Nrv, were used to screen a Drosophila embryo cDNA expression library , Three cDNA clones (designated Nrv1, Nrv2.1, and Nrv2.2) were isolate d that code for proteins recognized by anti-Nrv mAbs on Western blots, DNA sequencing and Southern blot analyses established that the cDNA c lones are derived from two different genes, rn situ hybridization to D rosophila polytene chromosomes showed that the cDNA clones map to the third chromosome near 92C-D, Nrv1 and Nrv2.1/2.2 have open reading fra mes of 309 and 322/323 amino acids, respectively; and they are 43.4% i dentical at the amino acid level. The proteins deduced from these clon es exhibit significant homology in both primary sequence and predicted topology to the beta subunit of Na+,K+-ATPase, Immunoaffinity-purifie d Nrv is associated with a protein (M(r) 100,000) recognized on Wester n blots by anti-ATPase alpha-subunit mAb. Our results suggest that the Drosophila nervous system-specific antigens Nrv1 and -2 are neuronal forms of the beta subunit of Na+,K+-ATPase.