Membrane topology of the <i>Drosophila</i> OR83b odorant receptor

By analogy to mammals, odorant receptors (ORs) in insects, such as Drosophila melanogaster , have long been thought to belong to the G‐protein coupled receptor (GPCR) superfamily. However, recent work has cast doubt on this assumption and has tentatively suggested an inverted topology compared to the canonical N out − C in 7 transmembrane (TM) GPCR topology, at least for some Drosophila ORs. Here, we report a detailed topology mapping of the Drosophila OR83b receptor using engineered glycosylation sites as topology markers. Our results are inconsistent with a classical GPCR topology and show that OR83b has an intracellular N‐terminus, an extracellular C‐terminus, and 7TM helices.