A family of peptidoglycan recognition proteins in the fruit fly Drosophilamelanogaster

Peptidoglycans from bacterial cell walls trigger immune responses in insect s and mammals. A peptidoglycan recognition protein, PGRP, has been cloned f rom moths as well as vertebrates and has been shown to participate in pepti doglycan-mediated activation of prophenoloxidase in the silk moth. Here we report that Drosophila expresses 12 PGRP genes, distributed in 8 chromosoma l loci on the 3 major chromosomes. By analyzing cDNA clones and genomic dat abases, we grouped them into two classes: PGRP-SA. SB1, SB2, SC1A, SC1B, SC 2, and SD, with short transcripts and short 5'-untranslated regions; and PC RP-LA, LB, LC, LD, and LE, with long transcripts and long 5'-untranslated r egions. The predicted structures indicate that the first group encodes extr acellular proteins and the second group, intracellular and membrane-spannin g proteins. Most PGRP genes are expressed in all postembryonic stages. Pept idoglycan injections strongly induce five of the genes. Transcripts from th e different PGRP genes were found in immune competent organs such as fat bo dy, gut, and hemocytes. We demonstrate that at least PGRP-SA and SC1B can b ind peptidoglycan, and a function in immunity is likely for this family.