HELIX-POMATIA LECTIN, AN INDUCER OF DROSOPHILA IMMUNE-RESPONSE, BINDSTO HEMOMUCIN, A NOVEL SURFACE MUCIN

We describe the isolation and initial characterization of hemomucin, a novel Drosophila surface mucin that is likely to be involved in the i nduction of antibacterial effector molecules after binding a snail lec tin (Helix pomatia A hemagglutinin). Two proteins of 100 and 220 kDa w ere purified from the membrane fraction of a Drosophila blood cell lin e using lectin columns. The two proteins are products of the same gene , as demonstrated by peptide sequencing. The corresponding cDNAs code for a product that contains an amino-terminal putative transmembrane d omain, a domain related to the plant enzyme strictosidine synthase, an d a mucin-like domain in the carboxyl-terminal part of the protein. Th e gene is expressed throughout development. In adult flies, high expre ssion is found in hemocytes, in specialized regions of the gut, and in the ovary, where the protein is deposited onto the egg surface. In th e gut, the mucin co-localizes with the peritrophic membrane. The cytog enetic location of the gene is on the third chromosome in the region 9 7F-98A.