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 mitochondri a mas functionally reconstituted as ATP/ADP exchange carrier in asolec tin/cardiolipin vesicles. The ANT preparations used were free of porin , cyclophilin D, and Bas as analysed immunologically and by activity m easurements. After pre-loading the ANT-containing proteoliposomes with ATP, malate or AMP, a gradual release of the trapped compounds by inc reasing the external Ca2+ concentrations could be demonstrated. N-Meth yl-Val-4-cyclosporin did not inhibit the Ca2+ dependent release of int ernal substances from ANT liposomes, This inhibitor,vas found to be sp ecific for the mitochondrial permeability transition pore (MTP) in int act mitochondria or reconstituted MTP-like protein complexes (e,g, hex okinase, porin, ANT complex). However, ADP in concentrations > 20 mu M inhibited the liberation of internal compounds, while in contrast, at ractyloside (30 mu M) and HgCl2 (5 mu M) both induced permeability of the ANT-containing liposomes resulting in a release of trapped substan ces. These results strongly suggest that ANT itself is capable to adop t a pore-like structure under conditions known to induce the permeabil ity transition in mitochondria, (C) 1998 Federation of European Bioche mical Societies.