Most insects, including human-targeting mosquitoes, detect odors through odorant-activated ion channel complexes consisting of a divergent odorant-binding subunit (OR) and a conserved co-receptor subunit (Orco). As a basis for understanding how odorants activate these heteromeric receptors, we report here cryo–electron microscopy structures of two different heteromeric odorant receptor complexes containing ORs from disease-vector mosquitos Aedes aegypti or Anopheles gambiae . These structures reveal an unexpected stoichiometry of one OR to three Orco subunits. Comparison of structures in odorant-bound and unbound states indicates that odorant binding to the sole OR subunit is sufficient to open the channel pore, suggesting a mechanism of OR activation and a conceptual framework for understanding evolution of insect odorant receptor sensitivity.

中文翻译：

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昆虫异聚气味受体气味感知的结构基础


大多数昆虫，包括以人类为目标的蚊子，通过气味剂激活的离子通道复合物检测气味，该复合物由不同的气味剂结合亚基（OR）和保守的共受体亚基（Orco）组成。作为了解气味剂如何激活这些异聚受体的基础，我们在此报告了两种不同的异聚气味受体复合物的冷冻电子显微镜结构，其中含有来自疾病媒介蚊子的OR埃及伊蚊或者冈比亚按蚊。这些结构揭示了一个 OR 至三个 Orco 亚基的意外化学计量。气味剂结合和未结合状态的结构比较表明，气味剂与唯一 OR 亚基的结合足以打开通道孔，这表明 OR 激活机制和理解昆虫气味受体敏感性进化的概念框架。