The Toll gene of drosophila, required for dorsal-ventral embryonic polarity, appears to encode a transmembrane protein

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The Toll gene of Drosophila, a maternal effect gene that plays a central role in the establishment of the embryonic dorsal-ventral pattern, has been cloned using P element tagging. A 5.3 kb poly(A) + ovarian transcript from the cloned region was purified by hybrid selection with the cloned DNA. This purified transcript complements the Toll mutant phenotype when injected into Toll − embryos, which proves that it is the Toll transcript. The sequence of cDNAs suggests that the Toll protein is an integral membrane protein with a cytoplasmic domain and a large extracytoplasmic domain. The putative extracytoplasmic domain contains at least 15 repeats of a 24 amino acid, leucinerich sequence found in both human and yeast membrane proteins.