Odorant-binding proteins (OBPs) of vertebrates belong to the lipocalin superfamily and perform a dual function: solubilizing and ferrying volatile pheromones to the olfactory receptors, and complexing the same molecules in specialized glands and assisting their release into the environment. Within vertebrates, to date they have been reported only in mammals, apart from two studies on amphibians. Based on the small number of OBPs expressed in each species, on their sites of production outside the olfactory area and their presence in biological fluids known to be pheromone carriers, such as urine, saliva and sexual secretions, we conclude that OBPs of mammals are specifically dedicated to pheromonal communication. This assumption is further supported by the observation that some OBPs present in biological secretions are endowed with their own pheromonal activity, adding renewed interest to these proteins. Another novel piece of evidence is the recent discovery that glycosylation and phosphorylation can modulate the binding activity of these proteins, improving their affinity to pheromones and narrowing their specificity. A comparison with insects and other arthropods shows a completely different scenario. While mammalian OBPs are specifically tuned to pheromones, those of insects, which are completely different in sequence and structure, include carriers for general odorants in addition to those dedicated to pheromones. Additionally, whereas mammals adopted a single family of carrier proteins for chemical communication, insects and other arthropods are endowed with several families of semiochemical-binding proteins. Here, we review the literature on the structural and functional properties of vertebrate OBPs, summarize the most interesting new findings and suggest possible exciting future developments.

中文翻译：

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哺乳动物的气味结合蛋白

脊椎动物的气味结合蛋白（OBP）属于脂质运载蛋白超家族，具有双重功能：溶解挥发性信息素并将其运送到嗅觉受体，并在专门的腺体中复合相同的分子并协助它们释放到环境中。在脊椎动物中，除了两项针对两栖动物的研究外，迄今为止仅在哺乳动物中报道过它们。基于每个物种中表达的 OBP 数量较少、其在嗅觉区域之外的产生位点以及它们存在于已知为信息素载体的生物体液中，例如尿液、唾液和性分泌物，我们得出结论，哺乳动物的 OBP 是特异的。致力于信息素通讯。这一假设得到了观察的进一步支持，即生物分泌物中存在的一些 OBP 被赋予了自己的信息素活性，从而增加了人们对这些蛋白质的新兴趣。另一个新的证据是最近发现糖基化和磷酸化可以调节这些蛋白质的结合活性，提高它们与信息素的亲和力并缩小它们的特异性。与昆虫和其他节肢动物的比较显示出完全不同的情况。哺乳动物的 OBP 专门针对信息素进行调节，而昆虫的 OBP 在序列和结构上完全不同，除了专门用于信息素的载体之外，还包括一般气味剂的载体。此外，哺乳动物采用单一载体蛋白家族进行化学通讯，而昆虫和其他节肢动物则具有多个化学信息结合蛋白家族。在这里，我们回顾了有关脊椎动物 OBP 的结构和功能特性的文献，总结了最有趣的新发现，并提出了可能令人兴奋的未来发展。