scholarly journals The utilization of iron and its complexes by mammalian mitochondria

1972 ◽  
Vol 128 (5) ◽  
pp. 1043-1055 ◽  
Author(s):  
R. Barnes ◽  
J. L. Connelly ◽  
O. T. G. Jones
Keyword(s):  
Mitochondrial Membrane ◽  
Nadh Dehydrogenase ◽  
Oxygen Electrode ◽  
Permeability Barrier ◽  
Antimycin A ◽  
Inner Mitochondrial Membrane ◽  
Mammalian Mitochondria ◽  
Ferrioxamine B ◽  
Lag Period ◽  
Subsequent Incorporation

Sonicated mitochondria catalyse the reduction of ferric salts, and the subsequent incorporation of Fe2+ into haem, when provided with a reducing substrate such as succinate or NADH. The rate of haem synthesis was low under aerobic conditions and, after a short lag period, accelerated once anaerobic conditions were achieved; it was insensitive to antimycin A. The lag period was decreased by preincubating the mitochondria with NADH and Fe3+. Newly formed Fe2+ was autoxidized rapidly and the consequent O2 uptake was measured with an oxygen electrode to determine the rate of enzymic formation of Fe2+ from FeCl3; this reaction was rapid in sonicated mitochondria provided with NADH or succinate and was insensitive to antimycin A. The reaction was very slow in intact mitochondria, suggesting a permeability barrier to Fe3+ ions. This system was used to test the permeability of the mitochondrial membrane to various iron complexes of biological importance. Of the compounds tested only ferrioxamine G appeared to penetrate readily and the iron of this complex was reduced when intact mitochondria were supplied with succinate or NADH-linked substrates. The reduction was insensitive to rotenone or antimycin A. Both ferrioxamine G and ferrioxamine B were, however, reduced by particles. The membrane fraction of sonicated mitochondria was necessary for the reduction. The rate of ferrioxamine B reduction by sonicated mitochondria was measured by a dual-wavelength spectrophotometric assay and was found to be stimulated in conditions where the Fe2+ produced was utilized for haem synthesis. The addition of FeCl3 to anaerobic particles caused an oxidation of cytochrome b when this region of the respiratory chain was isolated by treatment with rotenone and antimycin A. These results suggest that the reduction of ferric iron and its complexes occurs inside the inner mitochondrial membrane in proximity to ferrochelatase. Possible sites for this reduction are the flavoproteins, succinate and NADH dehydrogenase.

scholarly journals The organization of NADH dehydrogenase polypeptides in the inner mitochondrial membrane

1980 ◽  
Vol 185 (2) ◽  
pp. 315-326 ◽  
Author(s):  
S Smith ◽  
C I Ragan
Keyword(s):  
Complex I ◽  
Mitochondrial Membrane ◽  
Nadh Dehydrogenase ◽  
Inner Mitochondrial Membrane ◽  
Submitochondrial Particles ◽  
Cytoplasmic Face ◽  
The Matrix

The organization of the constituent polypeptides of mitochondrial NADH dehydrogenase was studied by using two membrane-impermeable probes, diazobenzene[35S]sulphonate and lactoperoxidase-catalysed radioiodination. The incorporation of label into the subunits of the isolated enzyme was compared with that obtained with enzyme immunoprecipitated from labelled mitochondria or inverted submitochondrial particles. On the basis of accessibility to these two labels, we divide the polypeptides of Complex I into five groups: those that are apparently buried in the enzyme, those that are accessible to labelling in the isolated enzyme but not in the membrane, those that are exposed on the cytoplasmic face of the membrane, those that are exposed on the matrix face and finally those that are exposed on both faces and are therefore transmembranous. We conclude that NADH dehydrogenase is asymmetrically organized across the inner mitochondrial membrane.

Modulation of the calcium-activated BK-channel of the inner mitochondrial membrane by hypoxia

2007 ◽  
Vol 34 (S 2) ◽  
Author(s):  
D Siemen ◽  
Y Cheng ◽  
X Gu ◽  
P Bednarczyk ◽  
GG Haddad ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Bk Channel ◽  
Inner Mitochondrial Membrane

The Efects of Spaceflight on Mitochondria in Human Lymphocytes (Jurkat).

1999 ◽  
Vol 5 (S2) ◽  
pp. 1118-1119
Author(s):  
Heide Schatten ◽  
Marian Lewis
Keyword(s):  
Mitochondrial Membrane ◽  
Space Shuttle ◽  
Human Lymphocytes ◽  
Jurkat Cells ◽  
Apoptotic Bodies ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Alterations ◽  
Mitochondrial Volume ◽  
Number Of Cells ◽  
Related Increase

Spaceflight induced mitochondrial alterations have been reported for muscle and may be associated with altered physiological functions in space. Mitochondrial alterations are also indicative of preapoptotic events which are seen in greater amounts in cells exposed to spaceflight when compared with cells cultured at 1 g. Preapoptotic mitochondrial changes include alterations of processes at the inner mitochondrial membrane and can result in changes in mitochondrial volume. Higher amounts of oxidative stress during space flight may be one of the causes for changes which lead to apoptosis. Jurkat cells flown on the STS-76 space shuttle mission showed an increase in the number of cells with apoptotic bodies early in the mission and a time-dependent, microgravity-related increase in the Fas/APO-1 cell death factor. Here we investigated the morphology of mitochondria in Jurkat cells exposed to spaceflight during the STS-76 mission.

scholarly journals Mitochondrial Fusion in Yeast Requires the Transmembrane GTPase Fzo1p

1998 ◽  
Vol 143 (2) ◽  
pp. 359-373 ◽  
Author(s):  
Greg J. Hermann ◽  
John W. Thatcher ◽  
John P. Mills ◽  
Karen G. Hales ◽  
Margaret T. Fuller ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Fusion Reaction ◽  
Point Mutations ◽  
Integral Membrane Protein ◽  
Mitochondrial Fusion ◽  
Inner Mitochondrial Membrane ◽  
Fusion Event ◽  
Gtpase Domain ◽  
Developmentally Regulated ◽  
Mitochondrial Reticulum

Membrane fusion is required to establish the morphology and cellular distribution of the mitochondrial compartment. In Drosophila, mutations in the fuzzy onions (fzo) GTPase block a developmentally regulated mitochondrial fusion event during spermatogenesis. Here we report that the yeast orthologue of fuzzy onions, Fzo1p, plays a direct and conserved role in mitochondrial fusion. A conditional fzo1 mutation causes the mitochondrial reticulum to fragment and blocks mitochondrial fusion during yeast mating. Fzo1p is a mitochondrial integral membrane protein with its GTPase domain exposed to the cytoplasm. Point mutations that alter conserved residues in the GTPase domain do not affect Fzo1p localization but disrupt mitochondrial fusion. Suborganellar fractionation suggests that Fzo1p spans the outer and is tightly associated with the inner mitochondrial membrane. This topology may be required to coordinate the behavior of the two mitochondrial membranes during the fusion reaction. We propose that the fuzzy onions family of transmembrane GTPases act as molecular switches to regulate a key step in mitochondrial membrane docking and/or fusion.

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