20S proteasome and protein oxidation in maize (Zea mays L.) leaves treated with cadmium

PENA LB; PASQUINI LA; GALLEGO SM

Pinamar-Argentina

Congreso; X PABMB Congress- XLI Annual Meeting of the Argentinean Society for Biochemistry and Molecular Biology Research; 2005

SAIB

Cadmium produces carbonylation of proteins. In order to test the possible involvement of the 20S proteasome on the degradation of oxidised proteins, we investigated in maize (Zea mays L.) leaf segments the effect of different cadmium concentration on activities, protein abundance and oxidation of the 20S proteasome. We also investigated the accumulation of carbonylated and ubiquitinated proteins. With a low Cd concentration (50 µM CdCl2), abundance of 20S proteasome protein remained similar to control, while trypsin- and PGPH-like activities were significantly increased. This increments in 20S proteasome activities were probably caused by the enhanced in 20S proteasome oxidation and was responsible for the degradation of oxidised proteins. When leaf segments were treated with higher cadmium concentration (100 and 200 µM CdCl2), 20S proteasome activity and protein abundance decreased, with a concomitant accumulation of carbonylated and ubiquitinated proteins. These results suggest that the 20S proteasome could be involved in secondary antioxidative defences, causing degradation of oxidised proteins in plant cells under oxidative stress generated by cadmium.