title: Protamine inhibition of the oxidative phosphorylation in intact, cytochrome c-depleted and restored mitochondria.
abstract: On the basis of polarographic data it is shown that protamine has a biphasic effect on the respiration of intact mitochondria. At lower protamine concentrations respiration is stimulated and this combined with a decrease of the respiratory control index; at higher ones respiration is inhibited and respiratory control is lost. In cytochrome c-depleted and restored mitochondria protamine effect on oxidative phosphorylation is only inhibitory. Increasing cytochrome c concentrations restore respiration in protamine-treated cytochrome c depleted mitochondria but not the respiratory control. Binding of cytochrome c to mitochondria is studied by determining from Scatchard plots the number of high affinity binding sites (n) and their stability constants (K). In absence of protamine in intact mitochondria n = 2.7 and K = 4.67-10(6) M-1; in cotochrome c depleted mitochondria n = 4.7 and K = 5.16-10(6) M-1. In both types of mitochondria protamine decreases significantly n as well as K. These data show that protamine may affect oxidative phosphorylation by causing desorption of cytochrome c from the inner mitochondrial membrane.
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D001665:Binding Sites; D003574:Cytochrome c Group / Q000172:deficiency; D008928:Mitochondria / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010101:Oxygen Consumption; D011479:Protamines / Q000494:pharmacology*
chemical_list: D003574:Cytochrome c Group; D011479:Protamines; D000244:Adenosine Diphosphate