Structural Transformation Detection Contributes to Screening of Behaviorally Active Compounds: Dynamic Binding Process Analysis of DhelOBP21 from Dastarcus helophoroides

Abstract

In light of reverse chemical ecology, the fluorescence competitive binding assays of functional odorant binding proteins (OBPs) is a recent advanced approach for screening behaviorally active compounds of insects. Previous research on Dastareus helophoroides identified a minus-C OBP, DhelOBP21, which preferably binds to several ligands. In this study, only (+)-β-pinene proved attractive to unmated adult beetles. To obtain a more in-depth explanation of the lack of behavioral activity of other ligands we selected compounds with high (camphor) and low (β-caryophyllene) binding affinities. The structural transformation of OBPs was investigated using well-established approaches for studying binding processes, such as fluorescent quenching assays, circular dichroism, and molecular dynamics. The dynamic binding process revealed that the flexibility of DhelOBP21 seems conducive to binding specific ligands, as opposed to broad substrate binding. The compound (+)-β-pinene and DhelOBP21 formed a stable complex through a secondary structural transformation of DhelOBP21, in which its amino-terminus transformed from random coil to an α-helix to cover the binding pocket. On the other hand, camphor could not efficiently induce a stable structural transformation, and its high binding affinities were due to strong hydrogen-bonding, compromising the structure of the protein. The other compound, β-caryophyllene, only collided with DhelOBP21 and could not be positioned in the binding pocket. Studying structural transformation of these proteins through examining the dynamic binding process rather than using approaches that just measure binding affinities such as fluorescence competitive binding assays can provide a more efficient and reliable approach for screening behaviorally active compounds.

The role of chemosensory protein 10 in the detection of behaviorally active compounds in brown planthopper, Nilaparvata lugens

“…It is persuasive that NlugCSP10 may contribute to the detection of cis ‐3‐hexenyl acetate communication. It has been reported that dsRNA treatment of Aenasius bambawalei also inhibited responses to volatiles (Li et al ., ), and similarly Dastarcus helophoroides was also non‐responsive to volatiles after dsRNA injection (Yang et al ., ). On the other hand, injection of dsNlugCSP10 did not show any effect on the behavioral responses of the BPH toward eicosane and (+)‐ β ‐pinene; it is likely that there are other CSPs and OBPs also participating in olfactory recognition in insects (Pelosi et al ., ; Zeng et al ., ).…”

Functional Analysis of Two Odorant-Binding Proteins, MaltOBP9 and MaltOBP10, in Monochamus alternatus Hope

“…MaltOBP10 is specifically expressed in the antenna of females and it may play a role in the fundamental olfactory recognition process. Fluorescence-binding assays have some shortcomings, for instance, high binding affinities showed by this experiment do not always mean the real binding between the OBP and the ligand, in some cases, that is the consequence of molecular collisions (Yang et al, 2017). Thus more information about the binding characteristics of OBPs, such as quenching analysis and secondary structural transformation, should be obtained in further experiments.…”

“…Moreover, the classical fluorescence competitive binding assay is the key technique for insect reverse chemical ecology by targeting OBPs to screen behaviorally active compounds of insects (Tsitsanou et al, 2012;Jayanthi et al, 2014;Brito et al, 2016). Using insect reverse chemical ecology methods, it was shown that (+)-β-pinene binds with DhelOBP21 and it is attractive to Dastarcus helophoroides (Yang et al, 2017), which is a major biological control agent against Monochamus alternatus Hope (Wei et al, 2009).…”

Structural investigation of selective binding dynamics for the pheromone‐binding protein 1 of the grapevine moth, Lobesia botrana

“…For instance, research on the Nuclear Magnetic Resonance (NMR) structure of the PBP1 of Antheraea polyphemus suggests that residues, such as Asn53 are involved in the initial recognition of pheromones probably via hydrogen bonds and Phe12, Phe36, Trp37, Phe76, and Phe118 as responsible for unspecific binding (Mohanty, Zubkov, & Gronenborn, ). More recently, research on the binding mechanism of DhelOBP21 of D. helophoroides supports the use of molecular dynamics simulations as a suitable approach to test the stability and semiochemical activity of chemical candidates (Yang et al, ). The authors were able to observe a bioactive compound, (+)‐β‐pinene, in a stable conformation during 110 ns of simulations.…”