Structural and Functional Characterization of One Unclassified Glutathione S-Transferase in Xenobiotic Adaptation of Leptinotarsa decemlineata

Abstract

Arthropod Glutathione S-transferases (GSTs) constitute a large family of multifunctional enzymes that are mainly associated with xenobiotic or stress adaptation. GST-mediated xenobiotic adaptation takes place through direct metabolism or sequestration of xenobiotics, and/or indirectly by providing protection against oxidative stress induced by xenobiotic exposure. To date, the roles of GSTs in xenobiotic adaptation in the Colorado potato beetle (CPB), a notorious agricultural pest of plants within Solanaceae, have not been well studied. Here, we functionally expressed and characterized an unclassified-class GST, LdGSTu1. The three-dimensional structure of the LdGSTu1 was solved with a resolution up to 1.8 Å by X-ray crystallography. The signature motif VSDGPPSL was identified in the “G-site”, and it contains the catalytically active residue Ser14. Recombinant LdGSTu1 was used to determine enzyme activity and kinetic parameters using 1-chloro-2, 4-dinitrobenzene (CDNB), GSH, p-nitrophenyl acetate (PNA) as substrates. The enzyme kinetic parameters and enzyme-substrate interaction studies demonstrated that LdGSTu1 could catalyze the conjugation of GSH to both CDNB and PNA, with a higher turnover number for CDNB than PNA. The LdGSTu1 enzyme inhibition assays demonstrated that the enzymatic conjugation of GSH to CDNB was inhibited by multiple pesticides, suggesting a potential function of LdGSTu1 in xenobiotic adaptation.

Functional and Structural Diversity of Insect Glutathione S-transferases in Xenobiotic Adaptation

“…In eukaryotes and aerobic prokaryotes, GSTs are grouped into at least four major protein families: cytosolic GSTs, mitochondrial GSTs, microsomal GSTs, and bacterial Fosfomycin-resistance proteins 40 , 42 , 58 - 59 . Mitochondrial GSTs are known as the kappa class in mammals and are mostly found in the mitochondrial matrix 60 and peroxisomes 61 .…”

“…Each monomer of a cytosolic GST is composed of an N-terminal domain (domain I) and C-terminal domain (domain II). N-terminal domain has β strands and α helices, and the C-terminal domain consists of helices 42 , 62 , 74 . Domain I exhibits the structurally conserved thioredoxin-like fold motif βαβαββα (Figure 3 A&C) 44 , 68 , 75 .…”

“…As phase II enzymes, GSTs detoxify chemical compounds through catalyzing nucleophilic attack by the thiol group in reduced glutathione (GSH) on a wide range of electrophilic substrates 37 , 40 , 41 . These substrates can be plant allelochemicals, pesticides, environmental pollutants, or byproducts of oxidative stress 40 , 42 . GSTs are also involved in the phase I detoxification process such as dehydrochlorination of 1,1,1-Trichloro-2,2-bis( p -chlorophenyl) ethane (DDT) to less toxic 1,l-Dichloro-2,2-bis( p -chlorophenyl) ethylene (DDE) 22 , 43 , 44 .…”

Toxicological and transcriptomic effects in Mythimna separata (Lepidoptera: Noctuidae) exposed to chlorantraniliprole and functional characterization of glutathione S‐transferases

“…Sigma GSTs are related to the conjugation of lipid peroxidation 52 and they can be induced by bacterial challenges 53 . The omega, zeta, and unclassified GSTs have antioxidant or detoxification activities 54–56 . Microsomal GSTs are trimeric, membrane‐bound proteins with different structures and origins from cytosolic GSTs 57,58 .…”

“…53 The omega, zeta, and unclassified GSTs have antioxidant or detoxification activities. [54][55][56] Microsomal GSTs are trimeric, membrane-bound proteins with different structures and origins from cytosolic GSTs. 57,58 A microsomal-class GST in Leptinotarsa decemlineata was induced by three insecticides.…”