tailieunhanh - Báo cáo khoa học: Effect of magnesium ions on the activity of the cytosolic NADH/cytochrome c electron transport system

Cytochromec(cyto-c), added to isolated mitochondria, activates the oxida-tion of extramitochondrial NADH and the generation of a membrane potential, both linked to the activity of the cytosolic NADH/cyto-celectron transport pathway. | Effect of magnesium ions on the activity of the cytosolic NADH cytochrome c electron transport system Gianluigi La Piana1 Vincenza Gorgoglione1 Daniela Laraspata1 Domenico Marzulli2 and Nicola E. Lofrumento1 1 Department of Biochemistry and Molecular Biology University of Bari Italy 2 Institute of Biomembranes and Bioenergetics IBBE - CNR University of Bari Italy Keywords cytosolic NADH oxidation magnesium ions and mitochondrialmembrane permeability mitochondria cytochrome c and apoptosis mitochondrial contact sites and respiration mitochondrial membrane potential Correspondence N. E. Lofrumento Department of Biochemistry and Molecular Biology University of Bari via Orabona 4 70126 Bari Italy Fax 39 80 5443317 Tel 39 80 5443325 E-mail Received 25 July 2008 revised 5 September 2008 accepted 14 October 2008 Cytochrome c cyto-c added to isolated mitochondria activates the oxidation of extramitochondrial NADH and the generation of a membrane potential both linked to the activity of the cytosolic NADH cyto-c electron transport pathway. The data presented in this article show that the protective effect of magnesium ions on the permeability of the mitochondrial outer membrane supported by previously published data correlates with the finding that in hypotonic but not isotonic medium magnesium promotes a differential effect on both the additional release of endogenous cyto-c and on the increased rate of NADH oxidation depending on whether it is added before or after the mitochondria. At the same time magnesium prevents or almost completely removes the binding of exogenously added cyto-c. We suggest that in physiological low-amplitude swelling magnesium ions may have the function together with other factors of modulating the amount of cyto-c molecules transferred from the mitochondrial intermembrane space into the cytosol required for the correct execution of the apoptotic programme and or the activation of the NADH cyto-c electron transport .