State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Proteomics & Mass Spectrometry Laboratory, Institute for the Animal Production System in the Mediterranean Environment-National Research Council, 80147 Napoli, Italy.
Proc Natl Acad Sci U S A. 2017 Nov 14;114(46):E9802-E9810. doi: 10.1073/pnas.1711437114. Epub 2017 Oct 23.
The giant panda belongs to the family of Ursidae; however, it is not carnivorous, feeding almost exclusively on bamboo. Being equipped with a typical carnivorous digestive apparatus, the giant panda cannot get enough energy for an active life and spends most of its time digesting food or sleeping. Feeding and mating are both regulated by odors and pheromones; therefore, a better knowledge of olfaction at the molecular level can help in designing strategies for the conservation of this species. In this context, we have identified the odorant-binding protein (OBP) repertoire of the giant panda and mapped the protein expression in nasal mucus and saliva through proteomics. Four OBPs have been identified in nasal mucus, while the other two were not detected in the samples examined. In particular, AimelOBP3 is similar to a subset of OBPs reported as pheromone carriers in the urine of rodents, saliva of the boar, and seminal fluid of the rabbit. We expressed this protein, mapped its binding specificity, and determined its crystal structure. Structural data guided the design and preparation of three protein mutants bearing single-amino acid replacements in the ligand-binding pocket, for which the corresponding binding affinity spectra were measured. We also expressed AimelOBP5, which is markedly different from AimelOBP3 and complementary in its binding spectrum. By comparing our binding data with the structures of bamboo volatiles and those of typical mammalian pheromones, we formulate hypotheses on which may be the most relevant semiochemicals for the giant panda.
大熊猫属于熊科，但它不是肉食性动物，几乎完全以竹子为食。由于大熊猫具有典型的肉食性消化器官，因此无法获得足够的能量来维持活跃的生活，大部分时间都在消化食物或睡觉。进食和交配都受到气味和信息素的调节；因此，更好地了解嗅觉在分子水平上的作用可以帮助设计保护这种物种的策略。在这种情况下，我们已经确定了大熊猫的气味结合蛋白 (OBP) 谱，并通过蛋白质组学在鼻粘液和唾液中绘制了蛋白质表达图谱。在鼻粘液中鉴定出了 4 种 OBP，而在检查的样本中没有检测到其他 2 种。特别是，AimelOBP3 与在啮齿动物尿液、野猪唾液和兔子精液中报道的作为信息素载体的一组 OBP 相似。我们表达了这种蛋白质，绘制了它的结合特异性，并确定了它的晶体结构。结构数据指导了设计和制备在配体结合口袋中具有单个氨基酸取代的三种蛋白质突变体，并测量了相应的结合亲和力谱。我们还表达了 AimelOBP5，它与 AimelOBP3 明显不同，在结合谱上互补。通过将我们的结合数据与竹子挥发物的结构和典型哺乳动物信息素的结构进行比较，我们提出了哪些可能是大熊猫最相关的半化学物质的假设。
