THE SAP47 GENE OF DROSOPHILA-MELANOGASTER CODES FOR A NOVEL CONSERVEDNEURONAL PROTEIN ASSOCIATED WITH SYNAPTIC TERMINALS

Proteins expressed specifically in neurons and transported to synaptic terminals are likely to constitute important molecular elements of ne rvous system function. In an effort to characterize synapse-associated proteins (SAPs) of Drosophila, we have isolated from a hybridoma libr ary several monoclonal antibodies (MABs) that selectively stain synapt ic terminals in immunohistochemical preparations. MAB nc46 binds to mo st but not all synaptic terminals of the Drosophila nervous system, it also recognizes a protein with homologous distribution in other dipte ran flies and binds to large parts of fish CNS. In Western blots the a ntibody labels a Drosophila brain protein of 47 kDa and cross-reacts w ith brain proteins from several species including insects, fish, mouse and man. From these data we conclude that the corresponding gene has been conserved in evolution at least among diptera. Using MAB nc46 and expression cloning we have identified the 'sap47' gene coding for the 'synapse-associated protein of 47 kDa' of Drosophila melanogaster. Se quence analysis of genomic and cDNA clones reveals the intron-exon str ucture of the gene and characterizes the complete open reading frames of two alternatively spliced transcripts. The sap47 gene is located in 89A8-B3 on chromosome 3R and codes for two almost identical inferred polypeptides of 347 and 351 amino acids with no significant sequence h omology to known proteins.