Department of Chemistry, Oklahoma State University, Stillwater, OK, 74078, USA.
Sci Rep. 2018 Nov 20;8(1):17105. doi: 10.1038/s41598-018-35509-x.
Lepidopteran male moths have an extraordinarily sensitive olfactory system that is capable of detecting and responding to minute amounts of female-secreted pheromones over great distances. Pheromone-binding proteins (PBPs) in male antennae ferry the hydrophobic ligand across the aqueous lymph to the olfactory receptor neuron triggering the response. PBPs bind ligands at physiological pH of the lymph and release them at acidic pH near the receptor while undergoing a conformational change. In Anthereae polyphemus PBP1, ligand binding to the hydrophobic pocket and its release is regulated by two biological gates: His70 and His95 at one end of the pocket and C-terminus tail at the other end. Interestingly, in Asian corn borer Ostrinia furnacalis PBP2 (OfurPBP2), critical residues for ligand binding and release are substituted in both biological gates. The impact of these substitutions on the ligand binding and release mechanism in OfurPBP2 is not known. We report here overexpression of soluble OfurPBP2 and structural characterization at high and low pH by circular dichroism (CD) and NMR. Ligand binding and ab initio model development were carried out with fluorescence and small-angle X-ray scattering (SAXS) respectively. OfurPBP2 in solution at pH 6.5 is homogeneous, well-folded and has a compact globular shape.
鳞翅目雄蛾具有极其敏感的嗅觉系统，能够在远距离检测和响应雌性分泌的微量信息素。雄蛾触角中的信息素结合蛋白（PBPs）将疏水性配体穿过水性淋巴液运送到嗅觉受体神经元，引发反应。PBPs 在淋巴液的生理 pH 值下结合配体，并在靠近受体的酸性 pH 值下释放它们，同时发生构象变化。在 Anthereae polyphemus PBP1 中，配体与疏水口袋的结合及其释放受到两个生物门控的调节：口袋一端的 His70 和 His95 以及另一端的 C 末端尾巴。有趣的是，在亚洲玉米螟 Ostrinia furnacalis PBP2（OfurPBP2）中，配体结合和释放的关键残基在两个生物门控中都被取代。这些取代对 OfurPBP2 中配体结合和释放机制的影响尚不清楚。我们在此报告了可溶性 OfurPBP2 的过表达，并通过圆二色性（CD）和 NMR 分别在高 pH 值和低 pH 值下进行了结构表征。配体结合和从头计算模型的开发分别通过荧光和小角 X 射线散射（SAXS）进行。在 pH 值为 6.5 的溶液中，OfurPBP2 是均相的、折叠良好的，具有紧凑的球形形状。
