Observing How Glutathione and S-Hexyl Glutathione Bind to Glutathione S-Transferase from Rhipicephalus (Boophilus) microplus

Abstract

Rhipicephalus (Boophilus) microplus is one of the most widespread ticks causing a massive loss to livestock production. The long-term use of acaracides rapidly develops acaracide resistance. In R. microplus, enhancing the metabolic activity of glutathione S-transferase (RmGST) is one of the mechanisms underlying acaracide resistance. RmGST catalyzes the conjugation of glutathione (GSH) to insecticides causing an easy-to-excrete conjugate. The active RmGST dimer contains two active sites (hydrophobic co-substrate binding site (H-site) and GSH binding site (G-site)) in each monomer. To preserve the insecticide efficacy, s-hexyl glutathione (GTX), a GST inhibitor, has been used as a synergist. To date, no molecular information on the RmGST-GSH/GTX complex is available. The insight is important for developing a novel RmGST inhibitor. Therefore, in this work, molecular dynamics simulations (MD) were performed to explore the binding of GTX and GSH to RmGST. GSH binds tighter and sits rigidly inside the G-site, while flexible GTX occupies both active sites. In GSH, the backbone mainly interacts with W8, R43, W46, K50, N59, L60, Q72, and S73, while its thiol group directs to Y7. In contrast, the aliphatic hexyl of GTX protrudes into the H-site and allows a flexible peptide core to form various interactions. Such high GTX flexibility and the protrusion of its hexyl moiety to the H-site suggest the dual role of GTX in preventing the conjugation reaction and the binding of acaracide. This insight can provide a better understanding of an important insecticide-resistance mechanism, which may in turn facilitate the development of novel approaches to tick control.

In Vivo Characterization of the Anti-Glutathione S-Transferase Antibody Using an In Vitro Mite Feeding Model

“…In this study, we analyzed the alpha-fold monomeric structures of GSTs isolated from avian mites. The predicted monomer of each GST contained eight helixes (α1–α8), four beta-strands (β1–β4), two active sites (G- and H-sites), and mu loop, and these features were similar to the monomer GST of R. microplus and allergens of other mite genera [ 63 , 64 ], with their sequence homology ranging from 46–53%. In addition, the GSTs of avian mites showed a function in catalyzing the conjugation of GSH to CDNB, similar to those reported previously [ 54 ].…”

“…The structure of GSTs of avian mites comprises two important domains: I at the N-terminus and II at the C-terminus, which are the general structures of GSTs of vertebrates and are required for their enzymatic function to detoxify and diminish the toxic effect of acaricides. In Rhipicephalus microplus , the active form of GSTs is a dimer, and each monomer contains eight helixes (α1–α8) and four beta-strands (β1–β4) [ 63 ]. In addition, GSTs, also known as allergens identified from Dermatophagoides pteronyssinus (house dust mite) and Tyrophagus putrescentiae mites, exhibit the dimer structure with eight helixes (α1–α8) and four beta-strands (β1–β4) [ 64 ].…”

Novel Inhibitor of Glutamate-Cysteine Ligase Catalytic Subunit against Tribolium castaneum: High-Throughout Virtual Screening, Molecular Docking and Dynamics Simulation, and Bioassay

“…CDOCKER is a molecular docking method based on the CHARMm force field, which can produce highly accurate docking results . In this round of screening, 225 selected compounds were docked into TcGclc binding sites using CDOCKER. , CDOCKER energy and CDOCKER interaction energy are the parameters reflected in the protein–ligand binding affinity . Here, 3 compounds with lower CDOCKER energy and CDOCKER interaction energy than BSO were selected (Table , Figure ).…”