Binding of magnesium by proteins of the mitochondrial intermembrane compartment

The intermembrane compartment of rat liver mitochondria contains high molecular weight compounds, most likely proteins, complexing magnesium ions. Compound/s/ of about 150 000 daltons has a low affinity /K_d 0.37 mM/ and a high binding capacity of 300 ng atoms Mg/mg protein; compound/s/ of about 100 000 daltons is characterized by a very high affinity towards magnesium /K_d of the order of magnitude of 0.001 mM/ and a low capacity of about 20 ng atoms Mg/mg protein.