Korrelation des unspezifisch permeablen mitochondrialen Raumes mit dem „Intermembran‐Raum”

Abstract

I .The term "unspecific permeability" in mitochondria is defined for describing a rapid equilibration of solutes between the extramitochondrial space and a portion of the intramitochondrial space. It appears to be a property of the outer membrane and is restricted only by the size of the molecule (maximal molecular weight of 5,000-12,000).2. The unspecifically permeable space varies considerably. It ranges from 20-80 Olio in different preparations of mitochondria. For a single mitochondrial preparation it is shown to be of equal volume for various small molecules such as sucrose, adenine nucleotides, NAD+ and aspartate.3. The total aqueous phase of rat liver mitochondria in isotonic sucrose medium ranges from 2.5-3.4 pllmg protein; the aqueous part of the impermeable space from 0.8-1.8 pl/mg protein.Only about I pl of this portion expands osmotically and represents the solvent for endogenous mitochondrial solutes. The major part (about 0.4-0.6 pl/mg protein) of the residual water of the impermeable space may be attributed to the hydrate shell of mitochondrial protein.4. The unspecifically permeable and the impermeable space of the mitochondria are compared with the morphologically defined intermembrane and matrix space. The tonicity of the incubation medium waa varied over a large range for rat liver and rat kidney mitochondria in order to facilitate this comparison. Large variations in the ratio of sucrose permeable to impermeable space (ranging from I : 3 in liver mitochondria to 3 : 1 in kidney mitochondria) correspond to changes in the ratio of the areas covered by the intermembrane and matrix space in the sections seen in the electron-micrographs. Mttochondria with low unspecific permeability are homogenous, mitochondria with high unspecific permeability show greater individual variability a t all tonicities.

Energy-Linked Ultrastructural Transformations in Isolated Liver Mitochondria and Mitoplasts

“…This is not surprising since the physiological level of K+ in intact freshly isolated liver mitochondria is approximately 150 µmoles/g of mitochondrial protein (41)(42)(43)(44)(45) and, together with its counteranions, chiefly total phosphates, accounts for the maintenance of the osmotic equilibrium of the inner compartment of liver 4 (12) also showed by light-scattering that the addition of glutaraldehyde to K+-loaded mitochondria did not change but rather stabilized the light-scattering signal and therefore did not cause change in the mitochondrial configuration during fixation . Lastly, only the condensed configuration of freshly isolated mitochondria, as observed after fixation in osmium tetroxide or glutaraldehyde, is compatible with the fact that freshly isolated mitochondria contain a compartment of sucrose-inaccessible water which is equal in volume to the inner compartment of the condensed configuration but is approximately one-half the volume of the inner compartment of the orthodox configuration (18,26,(46)(47)(48) . Passive osmotic volume changes also show conversion of the condensed to the orthodox configuration and its reversal by the controlled use of sucrose (30) .…”

Chloroplast Structure and Function in Tissue Cultures of a C4 Plant

“…The peripheral reticulum greatly increases the surface area of the inner membrane of the chloroplast envelope, and its involvement in the transport of materials across the envelope has been suggested (10). If the outer membrane were permeable and the inner membrane selectively permeable, as appears to be the case in mitochondria (12), and hence limiting to rapid transport across the envelope, a great increase of the limiting layer would be a logical way to facilitate transport. There is no compartmentalization of function in the cells of the callus, so the directed transport of photosynthates would not be expected.…”

Biogenesis of Cytochrome c in Neurospora crassa. Synthesis of Apocytochrome c, Transfer to Mitochondria and Conversion to Holocytochrome c

“…This appears to be a problem of major and general importance for protein transport into mitochondria. The outer membrane has been described to have pores for molecules with molecular weights up to 6000 to 10000 [25,26]. On the other hand, impermeability of the outer membrane to holocytochrome c has been observed with isolated mitochondria and outer membranes from rat liver [27,28].…”