115 个昆虫物种气味受体（OR）的序列、结构与对接谱多样性及 Orco 的结构特化
Class-wide sequence, structural, and docking-profile diversity of insect odorant receptors and structural specialization of Orco
研究整合序列相似性、结构相似性与分子对接，分析了 115 个昆虫物种的气味受体（OR），并发现 OR 库大小与成虫食性、幼虫食性和栖息地相关，而与昼夜节律无关。作者构建“主干–分支”网络框架，按序列与结构相似性对 OR 分类，并通过大规模分子对接得到比较对接谱；尽管序列与结构群组成差异明显，几乎所有采样目都含有可归入全部六个对接谱群的 OR。全变态昆虫的 OR 序列群多样性高于非全变态昆虫，对接谱组成在目级起源早于或晚于二叠纪末大灭绝的现存谱系间存在差异。
来源：eLife · doi.org
Insect olfaction is facilitated by a heterotetrameric odorant receptor–odorant receptor co-receptor (OR-Orco) complex. However, extensive sequence divergence and lineage-specific expansion have complicated large-scale comparisons of OR repertoires across insects. Here, we integrated sequence similarity, structural similarity, and molecular docking to analyze ORs from 115 insect species. OR repertoire size was associated with adult diet, larval diet, and habitat, but not with circadian rhythm. We developed a ‘trunk–branch’ network framework to classify ORs according to sequence and structural similarity and used large-scale molecular docking to derive comparative docking profiles. Despite marked differences in sequence- and structural-community composition, almost all sampled orders contained ORs assigned to all six docking-profile communities. Holometabolous insects showed higher OR sequence-community diversity than non-holometabolous insects, and docking-profile composition differed between extant lineages whose order-level origins predate or postdate the end-Permian mass extinction. Most notably, we identified a highly conserved extracellular β-sheet in Orco that restricts ligand access to the binding pocket and may contribute to its reduced capacity to bind natural odorants. The emergence of Orco represents a key evolutionary transition from homomeric receptors to heteromeric OR–Orco complexes, and our results suggest that this transition may have been accompanied by pronounced specialization of the extracellular domain and binding pocket. Together, these analyses provide a class-wide framework for comparing insect OR diversity and generate testable hypotheses for future experimental and evolutionary studies.