Substructure of inner mitochondrial membranes of myocardial cells as shown by cryo-ultramicrotomy

Summary The substructure of the inner mitochondrial membranes has been studied by cryo-ultramicrotomy under conditions during which denaturation of proteins by treatment with chemical solutes has been totally avoided. In such preparations, the inner membrane has a substructure consisting of globular subunits. These subunits have an average diameter of ca. 20Å–ca. 62Å and are fairly regularly spaced. Intracristal space is absent in the unstained, freeze-dried preparations, whereas a space of ca 40Å is seen in preparations lightly treated by OsO₄-vapour. It is concluded that the subunits of the inner mitochondrial membranes probably consist either of single protein molecules or of complexes of protein molecules.This work was supported by grants from The Norwegian Council on Cardiovascular Disease and from The Norwegian Research Council for Science and the Humanities