Chemoproteomics Prioritizes Mitochondrial ADP/ATP Translocase as a Candidate Target Associated with 6PPDQ-Induced Respiratory Toxicity in Rainbow Trout Gill
6PPD quinone (6PPDQ) is an emerging contaminant that induces acute respiratory toxicity in rainbow trout (Oncorhynchus mykiss), yet its underlying molecular mechanisms remain poorly understood. In the present study, short-term in vivo exposure of rainbow trout to 6PPDQ resulted in substantial accumulation and limited biotransformation of 6PPDQ in the gill, accompanied by pronounced gill structural damage and increased whole-fish oxygen consumption. Taking advantage of the electrophilic reactivity of the quinone moiety of 6PPDQ toward cysteine residues, we applied activity-based protein profiling (ABPP) to gill tissue. ABPP revealed marked alterations in mitochondrial cysteine reactivity and highlighted ADP/ATP translocase (ANT) as a candidate 6PPDQ-interacting mitochondrial protein. A Cys-160-containing ANT peptide within the nucleotide-binding domain of ANT was pinpointed as the covalent binding site through ABPP, Peptide-centric Local Stability Assay (PELSA), and molecular docking. Functional assays using isolated gill mitochondria showed that 6PPDQ elicited an uncoupling-like mitochondrial respiratory response that was partially attenuated by the ANT inhibitor carboxyatractyloside (CATR), supporting the functional involvement of ANT in this gill-based model. Together, these findings nominate ANT as a candidate gill mitochondrial target associated with 6PPDQ-induced acute respiratory toxicity and demonstrate the utility of chemoproteomics for prioritizing mechanistically relevant protein interactions of emerging pollutants.