The mitochondrial tricarboxylate carrier: Unexpected increased activity instarved silver eels

The tricarboxylate carrier was purified to homogeneity from liver mitochond ria of European eel at the silver and the yellow stage and functionally rec onstituted into liposomes. Unexpectedly, the molecular activity of the tric arboxylate carrier obtained from silver eel was about twofold higher than t hat of the same protein from yellow eel, although eels at the silver stage stop feeding. Parallel changes were found in the activities of the lipogeni c enzymes in silver eels. This suggests a functional coordination between a ll these proteins sequentially involved in hepatic lipogenesis. Cardiolipin added to proteoliposomes strongly stimulated the activity of the purified tricarboxylate carrier from yellow eels, whereas it slightly reduced the ac tivity of the same protein from silver eels. The higher activity of the tri carboxylate carrier from silver eels could therefore be ascribed, at least in part, to a different composition of the lipid domain surrounding the car rier protein, possibly in response to the hormonal alterations accompanying metamorphosis from yellow to silver stage. (C) 2000 Academic Press.