title: Structure-Based Analysis of the Ligand-Binding Mechanism for DhelOBP21, a C-minus Odorant Binding Protein, from Dastarcus helophoroides (Fairmaire; Coleoptera: Bothrideridae).
abstract: Odorant binding proteins (OBPs) transport hydrophobic odor molecules across the sensillar lymph to trigger a neuronal response. Herein, the Minus-C OBP (DhelOBP21) was characterized from Dastarcus helophoroides, the most important natural parasitic enemy insect that targets Monochamus alternatus. Homology modeling and molecular docking were conducted on the interaction between DhelOBP21 and 17 volatile molecules (including volatiles from pine bark, the larva of M. alternatus, and the faeces of the larva). The predicted three-dimensional structure showed only two disulfide bridges and a hydrophobic binding cavity with a short C-terminus. Ligand-binding experiments using N-phenylnaphthylamine (1-NPN) as a fluorescent probe showed that DhelOBP21 exhibited better binding affinities against those ligands with a molecular volume between 100 and 125 Å(³) compared with ligands with a molecular volume between 160 and 185 Å(³). Molecules that are too big or too small are not conducive for binding. We mutated the amino acid residues of the binding cavity to increase either hydrophobicity or hydrophilia. Ligand-binding experiments and cyber molecular docking assays indicated that hydrophobic interactions are more significant than hydrogen-bonding interactions. Although hydrogen-bond interactions could be predicted for some binding complexes, the hydrophobic interactions had more influence on binding following hydrophobic changes that affected the cavity. The orientation of ligands affects binding by influencing hydrophobic interactions. The binding process is controlled by multiple factors. This study provides a basis to explore the ligand-binding mechanisms of Minus-C OBP.
authors.affiliation: 1. Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, P. R. China.
authors.forename: Dong-Zhen
authors.initials: DZ
authors.lastname: Li
authors.affiliation: 2. College of Informatics, Huazhong Agricultural University, Wuhan 430070, P. R. China.
authors.forename: Guang-Qiang
authors.initials: GQ
authors.lastname: Yu
authors.affiliation: 1. Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, P. R. China.
authors.forename: Shan-Cheng
authors.initials: SC
authors.lastname: Yi
authors.affiliation: 3. Department of Horticulture, Beijing Vocational College of Agriculture, Beijing 102442, PR China.
authors.forename: Yinan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: 2. College of Informatics, Huazhong Agricultural University, Wuhan 430070, P. R. China.
authors.forename: De-Xin
authors.initials: DX
authors.lastname: Kong
authors.affiliation: 1. Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, P. R. China.
authors.forename: Man-Qun
authors.initials: MQ
authors.lastname: Wang
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D018035:Receptors, Odorant / Q000378:metabolism*
chemical_list: D018035:Receptors, Odorant; C045648:odorant-binding protein
keywords: Dastarcus helophoroides.; Odorant-binding proteins; fluorescence competitive binding assays; hydrophobic interactions; molecular docking; molecular volume; site-directed mutagenesis