Molecular basis for cysteine oxidation by Plant Cysteine Oxidases fromArabidopsis thaliana

Plant Cysteine Oxidases (PCOs) play important roles in controlling the stability of Group VII ethylene response factors (ERF-VIIs) via N-Arg/degron pathway through catalyzing the oxidation of their N-Cys for subsequent Arginyl-tRNA--protein transferase 1 (ATE1) mediated arginine installation. Here we presented structures of PCO2, PCO4, and PCO5 from Arabidopsis thaliana ( At PCOs) and examined their in vitro activity by MS. On the basis of Tris-bound At PCO2, we modelled the Cys-bound At PCO2 structure and identified key residues involved in N-Cys oxidation. Alanine substitution of potential N-Cys interaction residues impaired the activity of At PCO5 remarkably. The structural research, complemented by mutagenesis and mass spectrometry experiments, not only uncovers the substrate recognition and catalytic mode by At PCOs, but also sheds light on the future design of potent inhibitors for plant cysteine oxidases.