THE MITOCHONDRIAL SMALL HEAT-SHOCK-PROTEIN PROTECTS NADH-UBIQUINONE OXIDOREDUCTASE OF THE ELECTRON-TRANSPORT CHAIN DURING HEAT-STRESS IN PLANTS

Functional inactivation of the mitochondrial small heat-shock protein (lmw Hsp) in submitochondrial vesicles using protein-specific antibodi es indicated that this protein protects NADH:ubiquinone oxidoreductase (complex I), and consequently electron transport from complex I to cy tochrome c:O-2 oxidoreductase (complex IV). Lmw Hsp function completel y accounted for heat acclimation of complex I electron transport in pr e-heat-stressed plants. Addition of purified lmw Hsp to submitochondri al vesicles lacking this Hsp increased complex I electron transport ra tes 100% in submitochondrial vesicles assayed at high temperatures. Th ese results indicate that production of the mitochondrial Imw Hsp is a n important adaptation to heat stress in plants. (C) 1998 Federation o f European Biochemical Societies.