The tumour metabolism inhibitors GSAO and PENAO react with cysteines 57 and 257 of mitochondrial adenine nucleotide translocase

The two reactive ANT cysteine residues have been identified in this study by expressing cysteine mutants of human ANT1 in Saccharomyces cerevisiae and measuring interaction with the arsenical moiety of GSAO and PENAO. The arsenic atom of both compounds cross-links cysteine residues 57 and 257 of human ANT1.The sulphur atoms of these two cysteines are 20 ？ apart in the crystal structures of ANT and the optimal spacing of cysteine thiolates for reaction with As (III) is 3-4 ？. This implies that a significant conformational change in ANT is required for the organoarsenicals to react with cysteines 57 and 257. This conformational change may relate to the selectivity of the compounds for proliferating cells.Healthy cells mainly rely on oxidative phosphorylation to catabolise glucose, while cancer cells employ aerobic glycolysis to catabolise both glucose and glutamine [1]. Mitochondria coordinate the catabolism of glucose and glutamine in cancer cells so targeting this organelle has potential for the treatment of this disease. A promising molecular target is the hexokinase II-voltage dependent anion channel-adenine nucleotide translocase complex that spans the outer- and inner-mitochondrial membranes. This complex links glycolysis, oxidative phosphorylation and mitochondrial-mediated apoptosis in cancer cells.The first step in glycolysis, conversion of glucose and ATP to glucose-6-phosphate (G-6-P) and ADP, is catalyzed by hexokinase and cancer cells mostly employ an isoform (HKII) that is bound to mitochondria via interaction with the outer-membrane voltage dependent anion channel (VDAC) [2-5]. VDAC is associated with inner-membrane adenine nucleotide translocase (ANT), which exchanges matrix ATP for cytosolic ADP across the inner-membrane [6]. ANT is thought to have two functions in cancer cells: it provides ATP to hexokinase II, to phosphorylate and trap glucose in the cell [1], and is a component of the mitochondrial permeability transition pore [6], which is involve