The International Journal of Biochemistry & Cell Biology 32 (2000) 1093 – 1101 Possible involvement of the adenine nucleotide translocase in the activation of the permeability transition pore induced by cadmium Cecilia Zazueta *, Ce ´sar Sa ´nchez, Noemı ´ Garcı ´a, Francisco Correa Departamento de Bioquı ´mica, Instituto Nacional de Cardiologı ´a, Ignacio Cha ´ ez, Juan Badiano No. 1, Colonia Seccio ´n XVI, Me ´xico, D.F. 014080, Mexico Received 18 January 2000 Abstract Low levels of cadmium induce a rapid calcium efflux in energized rat kidney mitochondria. This is accompanied by the collapse of the transmembrane gradient in a partial CSA-sensitive fashion. The binding of 109 Cd 2 + to mitochondria is a saturable function; in the presence of NEM, the binding of 2.5 nmol 109 Cd 2 + /mg of protein suffices to induce the opening of the permeability transition pore. It was found that cadmium bound mainly to proteins of molecular weight between 30 and 50 kDa. In the presence of the monothiol reagent NEM, the label is concentrated in the 30 kDa protein. Following the addition of the reducing agent dithiothreitol, calcium is reaccumulated and the membrane potential restored. This correlates with a significant loss of label in the 30 kDa protein region. The 30 kDa protein was identified as the adenine nucleotide translocase by labelling experiments with eosin 5-maleimide and experiments of reconstitution. © 2000 Elsevier Science Ltd. All rights reserved. Keywords: Permeability transition; ADP/ATP carrier; Calcium efflux; Cadmium; Mitochondria www.elsevier.com/locate/ijbcb 1. Introduction The chemiosmotic hypothesis states that energy conservation, in mitochondria, depends on the maintenance of low conductance by the coupling membrane to solutes that are not transported by specific carriers [1]. Nevertheless, isolated mito- chondria can undergo a dramatic increase in per- meability after energy-dependent Ca 2 + load in the presence of a wide variety of inducing agents [2,3]. The inducing agents that convert critical thiol groups into disulfide bridges play a relevant role for the establishment of the increased perme- ability [4,5]. Heavy, or transition metal divalent cations, i.e. Cd 2 + or Pb 2 + , induce membrane leakiness most likely via the formation of coordi- nation complexes with two vicinal – SH groups. It has been reported that Cd 2 + induces pore open- ing through this mechanism. [3]. Abbreiations: CSA, cyclosporin A; ANT, adenine nucle- otide translocase; NEM, N-ethylmaleimide; RR, ruthenium red; DTT, dithiothreitol; RKM, rat kidney mitochondria. * Corresponding author. Fax: +1-915-55730926. E-mail address: zazueta22@hotmail.com (C. Zazueta). 1357-2725/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII:S1357-2725(00)00041-8