20S proteasome and accumulation of oxidized and ubiquitinated proteins in maize leaves subjected to cadmium stress

Cadmium toxicity is related to ROS production that then generates oxidized proteins, which are degraded afterwards by the 20S-proteasome (20S-P). Moderate oxidative stress generated by cadmium produces a slightly increased level of oxidized 20S protein. High metal concentration caused severe oxidative conditions, thereby decreasing 20S-proteasome activities, and concomitantly increasing oxidized and ubiquitinated proteins (Ub-P) accumulation.