Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, P. R. China.
Agricultural Bioinformatics Key Laboratory of Hubei Province, College of Informatics, Huazhong Agricultural University, Wuhan, 430070, P. R. China.
Sci Rep. 2018 Sep 10;8(1):13506. doi: 10.1038/s41598-018-31959-5.
Odorant-binding proteins (OBPs) play a pivotal role in transporting odorants through the sensillar lymph of insect chemosensory sensilla and increasing the sensitivity of the olfactory system. To address the ligand binding, activation, and release mechanisms of OBPs, we performed a set of conventional molecular dynamics simulations for binding of the odorant-binding protein DhelOBP21 from Dastarcus helophoroides with 18 ligands (1-NPN and 17 volatiles), as well as four constant-pH molecular dynamics simulations. We found that the open pocket DhelOBP21 at pH 5.0 could bind volatiles and form a closed pocket complex via transformation of its N-terminus into regular Helix at pH 7.0 and vice versa. Moreover, the discrimination of volatiles (selectivity and promiscuity) was determined by the characteristics of both the volatiles and the 'essential' and 'selective' amino acid residues in OBP binding pockets, rather than the binding affinity of the volatiles. This study put forward a new hypothesis that during the binding of volatiles there are two transitions for the DhelOBP21 amino-terminus: pH- and odorant binding-dependent random-coil-to-helix. Another important finding is providing a framework for the exploration of the complete coil-to-helix transition process and theoretically analyzing its underlying causes at molecular level.
气味结合蛋白（OBPs）在通过昆虫化学感觉感器的感觉淋巴运输气味物质和提高嗅觉系统的敏感性方面起着关键作用。为了解决 OBPs 的配体结合、激活和释放机制，我们对来自 Dastarcus helophoroides 的气味结合蛋白 DhelOBP21 与 18 种配体（1-NPN 和 17 种挥发性物质）以及 4 种恒 pH 分子动力学模拟进行了一组常规分子动力学模拟。我们发现，在 pH 5.0 时，开口口袋的 DhelOBP21 可以结合挥发性物质，并通过其 N 端转化为规则的螺旋形成封闭口袋复合物，反之亦然。此外，挥发性物质的区分（选择性和混杂性）取决于挥发性物质的特性以及 OBP 结合口袋中的“必需”和“选择性”氨基酸残基，而不是挥发性物质的结合亲和力。这项研究提出了一个新的假设，即在挥发性物质结合过程中，DhelOBP21 氨基末端有两个转变：pH 和气味物质结合依赖性无规卷曲到螺旋。另一个重要的发现是为探索完整的卷曲到螺旋转变过程提供了一个框架，并在分子水平上从理论上分析了其潜在原因。
