Reconstituted adenine nucleotide translocase forms a channel for small molecules comparable to the mitochondrial permeability transition pore

Highly purified adenylate translocase (ANT) from rat heart mitochondria mas functionally reconstituted as ATP/ADP exchange carrier in asolectin/cardiolipin vesicles. The ANT preparations used were free of porin, cyclophilin D, and Bas as analysed immunologically and by activity measurements. After pre-loading the ANT-containing proteoliposomes with ATP, malate or AMP, a gradual release of the trapped compounds by increasing the external Ca2+ concentrations could be demonstrated. N-Methyl-Val-4-cyclosporin did not inhibit the Ca2+ dependent release of internal substances from ANT liposomes, This inhibitor,vas found to be specific for the mitochondrial permeability transition pore (MTP) in intact mitochondria or reconstituted MTP-like protein complexes (e,g, hexokinase, porin, ANT complex). However, ADP in concentrations > 20 mu M inhibited the liberation of internal compounds, while in contrast, atractyloside (30 mu M) and HgCl2 (5 mu M) both induced permeability of the ANT-containing liposomes resulting in a release of trapped substances. These results strongly suggest that ANT itself is capable to adopt a pore-like structure under conditions known to induce the permeability transition in mitochondria, (C) 1998 Federation of European Biochemical Societies.