TRACE AMOUNTS OF TRITON X-100 MODIFY THE INHIBITOR SENSITIVITY OF THEMITOCHONDRIAL PORIN

Transport properties of mitochondrial porin were investigated on the b asis of changes in the activity of hexokinase utilizing external ATP. Production of glucose 6-phosphate is inhibited by polyanion both in in tact brain mitochondria and in contact point vesicles. Hexokinase acti vity is restored by solubilization of the enzyme by high ionic strengt h or 0.5-1% Triton X-100. In very low concentrations (0.001-0.005%) Tr iton does not mobilize hexokinase from its binding sites but it is abl e to release polyanion-inhibition completely. This finding provides an explanation for the discrepancy observed in the transport properties of porin when studied 'in situ' or in artificial lipid membranes.