Structural and Functional Insights into a Honey Bee Omega-Class Glutathione S-Transferase Mediating Chemical Sequestration and Antioxidative Stress

The European honey bee (Apis mellifera L.) is an essential crop pollinator and is frequently exposed to pesticide residues that may compromise bee health. Mechanisms underlying chemical adaptation and detoxification in honey bees remain incompletely understood, particularly those involving glutathione S-transferases (GSTs). Here, we structurally and functionally characterized omega-class GST AmGSTO1. AmGSTO1 was highly expressed in the fat bodies of nurse and forager bees. X-ray crystallography resolved the glutathione (GSH)-bound AmGSTO1 structure, revealing an active-site cysteine characteristic of omega GSTs. Enzyme assays showed greater catalytic efficiency toward the thioltransferase substrate HED than toward CDNB or PNA. Disc diffusion and bacterial survival assays demonstrated antioxidant activity against cumene hydroperoxide, hydrogen peroxide, and paraquat. Fluorescence binding assays indicated agrochemical binding, while HPLC detected no significant substrate depletion, suggesting a sequestration rather than catalytic role. Overall, AmGSTO1 may contribute to the protection against agrochemical toxicity and oxidative stress in honey bees.