scholarly journals Evolution of energy metabolism. Proton permeability of the inner membrane of liver mitochondria is greater in a mammal than in a reptile

1991 ◽  
Vol 275 (1) ◽  
pp. 81-86 ◽  
Author(s):  
M D Brand ◽  
P Couture ◽  
P L Else ◽  
K W Withers ◽  
A J Hulbert
Keyword(s):  
Metabolic Rate ◽  
Mitochondrial Membrane ◽  
Mitochondrial Protein ◽  
Rat Hepatocytes ◽  
Liver Mitochondria ◽  
Standard Metabolic Rate ◽  
Proton Permeability ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Bearded Dragon

Standard metabolic rate is 7-fold greater in the rat (a typical mammal) than in the bearded dragon, Amphibolurus vitticeps (a reptile with the same body mass and temperature). Rat hepatocytes respire 4-fold faster than do hepatocytes from the lizard. The inner membrane of isolated rat liver mitochondrial has a proton permeability that is 4-5-fold greater than the proton permeability of the lizard liver mitochondrial membrane per mg of mitochondrial protein. The greater permeability of rat mitochondria is not caused by differences in the surface area of the mitochondrial inner membrane, but differences in the fatty acid composition of the mitochondrial phospholipids may be involved in the permeability differences. Greater proton permeability of the mitochondrial inner membrane may contribute to the greater standard metabolic rate of mammals.

scholarly journals The uptake of silicic acid by rat liver mitochondria

1978 ◽  
Vol 172 (3) ◽  
pp. 557-568 ◽  
Author(s):  
R N Johnson ◽  
B E Volcani
Keyword(s):  
Silicic Acid ◽  
Diffusion Mechanism ◽  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Energy Status ◽  
Matrix Space ◽  
Inner Membrane ◽  
Simple Diffusion ◽  
Mitochondrial Inner Membrane

1. To gain insight into a putative role for mitochondria in silicon metabolism, mitochondrial uptake (by which it is meant the removal from the medium) of silicic acid [Si(OH)4] was studied under conditions minimizing SI(OH)4 polymerization. 2. Measurements of mitochondrial respiration and swelling indicated indirectly a significant uptake of Si(OH)4 as a weak acid, but this was not confirmed when 31Si(OH)4 was used as a tracer. 31Si(OH)4 occupied a mitochondrial volume similar to that of 3H2O and was relatively unaffected by mitochondrial energy status and by the pH gradient across the mitochondrial inner membrane. 3. Uptake was directly proportional to Si(OH)4 concentration in the range 0-3 mM. 4. The uptake consisted of two components: under all conditions examined, the greater quantity, amounting to 1-2nmol of Si(OH)4/mg of mitochondrial protein, was bound, a major portion of it external to the inner membrane, with the lesser quantity free within the matrix space. 5. Equilibration of 31Si(OH)4 between medium and matrix was a slow process, having a half-time of approx. 10 min at 22 degrees C. 6. Mersalyl and N-ethylmaleimide inhibited the uptake by preferentially lowering the amount of Si(OH)4 bound. Their action was somewhat variable, depending on the precise nature of the suspending medium, and suggesting that the bound material may represent polymerized forms of Si(OH)4. 7. It is concluded that Si(OH)4 may penetrate the mitochondrial inner membrane by a simple diffusion mechanism.

Contribution of mitochondrial proton leak to skeletal muscle respiration and to standard metabolic rate

1996 ◽  
Vol 271 (4) ◽  
pp. C1380-C1389 ◽  
Author(s):  
D. F. Rolfe ◽  
M. D. Brand
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Rate ◽  
Respiration Rate ◽  
Rat Hepatocytes ◽  
Standard Metabolic Rate ◽  
Proton Leak ◽  
Rat Skeletal Muscle ◽  
Isolated Rat Hepatocytes ◽  
Mitochondrial Inner Membrane

We have tested the hypothesis that the leak of protons across the mitochondrial inner membrane (proton leak) is a significant contributor to standard metabolic rate (SMR). We found that proton leak accounts for around one-half of the resting respiration rate of perfused rat skeletal muscle. Proton leak is known to make a significant (26%) contribution to the resting respiration rate of isolated rat hepatocytes (M. D. Brand, L.-F. Chien, E. K. Ainscow, D. F. S. Rolfe, and R. K. Porter. Biochim. Biophys. Acta 1187: 132-139, 1994). If the importance of proton leak in these isolated and perfused systems is similar to its importance in vivo, then using literature values for the contribution of liver and skeletal muscle to SMR, we can calculate that proton leak in liver and skeletal muscle alone accounts for 11-26% (mean 20%) of the SMR of the rat. If proton leak activity in the other tissues of the rat is similar to that in liver cells, then the contribution of proton leak to rat SMR would be 16-31% (mean 25%).

scholarly journals Characterization of Mmp37p, aSaccharomyces cerevisiaeMitochondrial Matrix Protein with a Role in Mitochondrial Protein Import

2006 ◽  
Vol 17 (9) ◽  
pp. 4051-4062 ◽  
Author(s):  
Michelle R. Gallas ◽  
Mary K. Dienhart ◽  
Rosemary A. Stuart ◽  
Roy M. Long
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Close Proximity ◽  
The Matrix ◽  
Targeting Signal

Many mitochondrial proteins are encoded by nuclear genes and after translation in the cytoplasm are imported via translocases in the outer and inner membranes, the TOM and TIM complexes, respectively. Here, we report the characterization of the mitochondrial protein, Mmp37p (YGR046w) and demonstrate its involvement in the process of protein import into mitochondria. Haploid cells deleted of MMP37 are viable but display a temperature-sensitive growth phenotype and are inviable in the absence of mitochondrial DNA. Mmp37p is located in the mitochondrial matrix where it is peripherally associated with the inner membrane. We show that Mmp37p has a role in the translocation of proteins across the mitochondrial inner membrane via the TIM23-PAM complex and further demonstrate that substrates containing a tightly folded domain in close proximity to their mitochondrial targeting sequences display a particular dependency on Mmp37p for mitochondrial import. Prior unfolding of the preprotein, or extension of the region between the targeting signal and the tightly folded domain, relieves their dependency for Mmp37p. Furthermore, evidence is presented to show that Mmp37 may affect the assembly state of the TIM23 complex. On the basis of these findings, we hypothesize that the presence of Mmp37p enhances the early stages of the TIM23 matrix import pathway to ensure engagement of incoming preproteins with the mtHsp70p/PAM complex, a step that is necessary to drive the unfolding and complete translocation of the preprotein into the matrix.

scholarly journals Uptake of protoporphyrin IX by isolated rat liver mitochondria

1980 ◽  
Vol 188 (2) ◽  
pp. 329-335 ◽  
Author(s):  
M E Koller ◽  
I Romslo
Keyword(s):  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Protoporphyrin Ix ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Erythropoietic Protoporphyria ◽  
Inner Membrane ◽  
Isolated Rat Liver ◽  
Isolated Rat

Rat liver mitochondria accumulate protoporphyrin IX from the suspending medium into the inner membrane in parallel with the magnitude of the transmembrane K+ gradient (K+in/K+out). Only protoporphyrin IX taken up in parallel with the transmembrane K+ gradient is available for haem synthesis. Coproporphyrins (isomers I and III) are not taken up by the mitochondria. The results support the suggestion by Elder & Evans [(1978) Biochem. J. 172, 345-347] that the prophyrin to be taken up by the inner mitochondrial membrane belongs to the protoporphyrin(ogen) IX series. Protoporphyrin IX at concentrations above 15 nmol/mg of protein has detrimental effects on the structural and functional integrity of the mitochondria. The relevance of these effects to the hepatic lesion in erythropoietic protoporphyria is discussed.

scholarly journals ‘Pore’ formation is not required for the hydroperoxide-induced Ca2+ release from rat liver mitochondria

1992 ◽  
Vol 285 (1) ◽  
pp. 65-69 ◽  
Author(s):  
J Schlegel ◽  
M Schweizer ◽  
C Richter
Keyword(s):  
Rat Liver ◽  
Pore Formation ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Specific Permeability ◽  
Specific Pathway

It has recently been suggested by several investigators that the hydroperoxide- and phosphate-induced Ca2+ release from mitochondria occurs through a non-specific ‘pore’ formed in the mitochondrial inner membrane. The aim of the present study was to investigate whether ‘pore’ formation actually is required for Ca2+ release. We find that the t-butyl hydroperoxide (tbh)-induced release is not accompanied by stimulation of sucrose entry into, K+ release from, and swelling of mitochondria provided re-uptake of the released Ca2+ (‘Ca2+ cycling’) is prevented. We conclude that (i) the tbh-induced Ca2+ release from rat liver mitochondria does not require ‘pore’ formation in the mitochondrial inner membrane, (ii) this release occurs via a specific pathway from intact mitochondria, and (iii) a non-specific permeability transition (‘pore’ formation) is likely to be secondary to Ca2+ cycling by mitochondria.

scholarly journals Mitochondrial Membrane Dynamics—Functional Positioning of OPA1

Antioxidants ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 186 ◽  
Author(s):  
Hakjoo Lee ◽  
Yisang Yoon
Keyword(s):  
Mitochondrial Membrane ◽  
Proteolytic Cleavage ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Functional Differences ◽  
New Information ◽  
New Development

The maintenance of mitochondrial energetics requires the proper regulation of mitochondrial morphology, and vice versa. Mitochondrial dynamins control mitochondrial morphology by mediating fission and fusion. One of them, optic atrophy 1 (OPA1), is the mitochondrial inner membrane remodeling protein. OPA1 has a dual role in maintaining mitochondrial morphology and energetics through mediating inner membrane fusion and maintaining the cristae structure. OPA1 is expressed in multiple variant forms through alternative splicing and post-translational proteolytic cleavage, but the functional differences between these variants have not been completely understood. Recent studies generated new information regarding the role of OPA1 cleavage. In this review, we will first provide a brief overview of mitochondrial membrane dynamics by describing fission and fusion that are mediated by mitochondrial dynamins. The second part describes OPA1-mediated fusion and energetic maintenance, the role of OPA1 cleavage, and a new development in OPA1 function, in which we will provide new insight for what OPA1 does and what proteolytic cleavage of OPA1 is for.

scholarly journals Calcium-dependent opening of a non-specific pore in the mitochondrial inner membrane is inhibited at pH values below 7. Implications for the protective effect of low pH against chemical and hypoxic cell damage

1991 ◽  
Vol 278 (3) ◽  
pp. 715-719 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Protective Effect ◽  
Adenine Nucleotide ◽  
Cell Damage ◽  
Liver Mitochondria ◽  
Low Ph ◽  
Hypoxic Cell ◽  
Inner Membrane ◽  
Calcium Dependent ◽  
Mitochondrial Inner Membrane ◽  
The Matrix

1. The rate of opening of the Ca(2+)-induced non-specific, cyclosporin A-inhibited, pore of the mitochondrial inner membrane of rat heart and liver mitochondria at pH 6.0 was less than 10% of that at pH 7.4. 2. The effect could not be explained by inhibition of Ca2+ uptake into the mitochondria, or of the matrix peptidyl-prolyl cis-trans isomerase (PPIase), or of the Ca(2+)-induced conformational change of the adenine nucleotide translocase. 3. It is suggested that the proposed interaction of matrix PPIase with the ‘c’ conformation of the adenine nucleotide carrier in the presence of Ca2+ [Griffiths & Halestrap (1991) Biochem. J. 274, 611-614] is inhibited by low pH. 4. The relevance of this to the protective effect of low pH on hypoxic and chemical-induced cell damage is discussed.

scholarly journals MAS6 encodes an essential inner membrane component of the yeast mitochondrial protein import pathway

1993 ◽  
Vol 122 (5) ◽  
pp. 1003-1012 ◽  
Author(s):  
JL Emtage ◽  
RE Jensen
Keyword(s):  
Protein Import ◽  
Early Stage ◽  
Osmotic Shock ◽  
Alkali Treatment ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

To identify new components that mediate mitochondrial protein import, we analyzed mas6, an import mutant in the yeast Saccharomyces cerevisiae. mas6 mutants are temperature sensitive for viability, and accumulate mitochondrial precursor proteins at the restrictive temperature. We show that mas6 does not correspond to any of the presently identified import mutants, and we find that mitochondria isolated from mas6 mutants are defective at an early stage of the mitochondrial protein import pathway. MAS6 encodes a 23-kD protein that contains several potential membrane spanning domains, and yeast strains disrupted for MAS6 are inviable at all temperatures and on all carbon sources. The Mas6 protein is located in the mitochondrial inner membrane and cannot be extracted from the membrane by alkali treatment. Antibodies to the Mas6 protein inhibit import into isolated mitochondria, but only when the outer membrane has been disrupted by osmotic shock. Mas6p therefore represents an essential import component located in the mitochondrial inner membrane.

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