Two Forms of a Mitochondrial Endonuclease in Neurospora crassa

1975 ◽  
Vol 53 (7) ◽  
pp. 823-825 ◽  
Author(s):  
Charles E. Martin ◽  
Robert P. Wagner
Keyword(s):  
Molecular Weight ◽  
Neurospora Crassa ◽  
Mitochondrial Membrane ◽  
Nuclease Activity ◽  
Inner Mitochondrial Membrane ◽  
Detergent Treatment ◽  
Approximate Molecular Weight ◽  
Membrane Bound

Mitochondrial nuclease activity in Neurospora crassa occurs in membrane-bound and soluble forms in approximately equal proportions. These activities apparently are due to the same enzyme, which has an approximate molecular weight of 120 000. A portion of the insoluble enzyme appears to be associated with the inner mitochondrial membrane and is resistant to solubilization by detergent treatment as well as by physical disruption methods.

scholarly journals Molecular mechanism of mitochondrial phosphatidate transfer by Ups1

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Jiuwei Lu ◽  
Chun Chan ◽  
Leiye Yu ◽  
Jun Fan ◽  
Fei Sun ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Mitochondrial Membrane ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Membranes ◽  
Inner Mitochondrial Membrane ◽  
Membrane Interaction ◽  
Detailed Mechanism ◽  
Physiological Regulator ◽  
Membrane Bound ◽  
Dynamics Simulations

AbstractCardiolipin, an essential mitochondrial physiological regulator, is synthesized from phosphatidic acid (PA) in the inner mitochondrial membrane (IMM). PA is synthesized in the endoplasmic reticulum and transferred to the IMM via the outer mitochondrial membrane (OMM) under mediation by the Ups1/Mdm35 protein family. Despite the availability of numerous crystal structures, the detailed mechanism underlying PA transfer between mitochondrial membranes remains unclear. Here, a model of Ups1/Mdm35-membrane interaction is established using combined crystallographic data, all-atom molecular dynamics simulations, extensive structural comparisons, and biophysical assays. The α2-loop, L2-loop, and α3 helix of Ups1 mediate membrane interactions. Moreover, non-complexed Ups1 on membranes is found to be a key transition state for PA transfer. The membrane-bound non-complexed Ups1/ membrane-bound Ups1 ratio, which can be regulated by environmental pH, is inversely correlated with the PA transfer activity of Ups1/Mdm35. These results demonstrate a new model of the fine conformational changes of Ups1/Mdm35 during PA transfer.

scholarly journals A method for determining the adenosine triphosphatase content of energy-transducing membranes. reaction of 4-chloro-7-nitrobenzofurazan with the adenosine triphosphatase of bovine heart submitochondrial particles

1976 ◽  
Vol 159 (2) ◽  
pp. 347-353 ◽  
Author(s):  
S J Ferguson ◽  
W J Lloyd ◽  
G K Radda
Keyword(s):  
Mitochondrial Membrane ◽  
Adenosine Triphosphatase ◽  
Plasma Membranes ◽  
Single Amino Acid ◽  
Mitochondrial Atpase ◽  
Inner Mitochondrial Membrane ◽  
Submitochondrial Particles ◽  
Bovine Heart ◽  
Single Amino Acid Residue ◽  
Membrane Bound

1. Modification of a single amino acid residue by introduction of the nitrobenzofurazan group inactivates mitochondrial ATPase (adenosine triphosphatase) when membrane-bound in submitochondrial particles. The similarity between the reactions of both membrane-bound and isolated ATPase with 4-chloro-7-nitrobenzofurazan indicates that the single essential tryosine residue identified in the isolated enzyme [Ferguson, Loyd, Lyons & Radda (1975) Eur. J. Biochem. 54, 117-126] Is also a feature of the membrane-bound ATPase. 2. A procedure is presented for estimating the ATPase content of the inner mitochondrial membrane. It is based on the specificity of the incorporation of the nitrobenzofurazan group, and the ready removal of this group by compounds that contain a thiol group. This method indicates that 8.5% of the membrane protein is ATPase. The procedure should be applicable to the titration of the energy-transducing ATPases of bacterial plasma membranes and of the thylakoid membranes of chloroplasts. 3. Combination of the data obtained on the ATPase content of the bovine heart inner mitochondrial membrane with a titration of the cytochrome bc1 complex with antimycin indicates that these two components of the membrane are present in approximately equal amounts.

SOLUBILIZATION AND PARTIAL CHARACTERIZATION OF HUMAN AND PORCINE THYROTROPHIN RECEPTORS

1978 ◽  
Vol 78 (1) ◽  
pp. 89-102 ◽  
Author(s):  
P. J. D. DAWES ◽  
V. B. PETERSEN ◽  
B. REES SMITH ◽  
R. HALL
Keyword(s):  
Molecular Weight ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Binding Activity ◽  
Human Thyroid ◽  
Scatchard Analysis ◽  
Binding Characteristics ◽  
Approximate Molecular Weight ◽  
Membrane Bound ◽  
Triton X

Thyrotrophin (TSH) receptors have been extracted from human and porcine thyroid membranes by treatment with Triton X-100.125I-Labelled bovine TSH was used to monitor receptor activity. Analysis by gel filtration and electrophoresis on acrylamide gels containing sodium dodecyl sulphate suggested that Triton extracts of human thyroid membranes contained TSH receptors with a molecular weight in the region of 50 000 closely associated with Triton micelles of approximate molecular weight 300 000. Isoelectric focusing studies indicated that the Triton-solubilized TSH binding activity had an isoelectric point of pH 4–4·5. The soluble TSH receptors were heat-labile, showed optimum TSH binding at pH 7·4 and reduced hormone binding at high ionic strength. The TSH binding characteristics of membrane-bound and solubilized human TSH receptors were similar and both preparations gave curved Scatchard plots. Solubilized porcine TSH receptors appeared to have a similar molecular weight to the human receptors and were also closely associated with Triton micelles of approximate molecular weight 300 000. Scatchard analysis of TSH binding to membrane-bound or solubilized porcine TSH receptors gave approximately linear plots with association constants of 2·8 ± 0·95 (s.e.m.) × 109 and 1·7 ± 0·27 × 1091/mol respectively. Comparison of the binding capacities of the solubilized and membrane-bound porcine receptors indicated that the 0·5% Triton extracts contained 40% of the original TSH binding activity and that this was present at a concentration of 25 ng/ml.

scholarly journals Biosynthetic pathway of mitochondrial ATPase subunit 9 in Neurospora crassa.

1983 ◽  
Vol 96 (1) ◽  
pp. 248-255 ◽  
Author(s):  
B Schmidt ◽  
B Hennig ◽  
R Zimmermann ◽  
W Neupert
Keyword(s):  
Molecular Weight ◽  
Mitochondrial Membrane ◽  
Proteolytic Cleavage ◽  
Mitochondrial Atpase ◽  
Inner Mitochondrial Membrane ◽  
Intact Cells ◽  
Atpase Subunit ◽  
Free System ◽  
Reticulocyte Lysates ◽  
Subunit 9

Subunit 9 of mitochondrial ATPase (Su9) is synthesized in reticulocyte lysates programmed with Neurospora poly A-RNA, and in a Neurospora cell free system as a precursor with a higher apparent molecular weight than the mature protein (Mr 16,400 vs. 10,500). The RNA which directs the synthesis of Su9 precursor is associated with free polysomes. The precursor occurs as a high molecular weight aggregate in the postribosomal supernatant of reticulocyte lysates. Transfer in vitro of the precursor into isolated mitochondria is demonstrated. This process includes the correct proteolytic cleavage of the precursor to the mature form. After transfer, the protein acquires the following properties of the assembled subunit: it is resistant to added protease, it is soluble in chloroform/methanol, and it can be immunoprecipitated with antibodies to F1-ATPase. The precursor to Su9 is also detected in intact cells after pulse labeling. Processing in vivo takes place posttranslationally. It is inhibited by the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). A hypothetical mechanism is discussed for the intracellular transfer of Su9. It entails synthesis on free polysomes, release of the precursor into the cytosol, recognition by a receptor on the mitochondrial surface, and transfer into the inner mitochondrial membrane, which is accompanied by proteolytic cleavage and which depends on an electrical potential across the inner mitochondrial membrane.

scholarly journals Bax Is Present as a High Molecular Weight Oligomer/Complex in the Mitochondrial Membrane of Apoptotic Cells

2001 ◽  
Vol 276 (15) ◽  
pp. 11615-11623 ◽  
Author(s):  
Bruno Antonsson ◽  
Sylvie Montessuit ◽  
Belen Sanchez ◽  
Jean-Claude Martinou
Keyword(s):  
Molecular Weight ◽  
Membrane Protein ◽  
Hela Cells ◽  
Mitochondrial Membrane ◽  
Outer Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Voltage Dependent Anion Channel ◽  
Large Molecular Weight ◽  
Mitochondrial Membrane Protein

Bax is a Bcl-2 family protein with proapoptotic activity, which has been shown to trigger cytochromecrelease from mitochondria bothin vitroandin vivo. In control HeLa cells, Bax is present in the cytosol and weakly associated with mitochondria as a monomer with an apparent molecular mass of 20,000 Da. After treatment of the HeLa cells with the apoptosis inducer staurosporine or UV irradiation, Bax associated with mitochondria is present as two large molecular weight oligomers/complexes of 96,000 and 260,000 Da, which are integrated into the mitochondrial membrane. Bcl-2 prevents Bax oligomerization and insertion into the mitochondrial membrane. The outer mitochondrial membrane protein voltage-dependent anion channel and the inner mitochondrial membrane protein adenosine nucleotide translocator do not coelute with the large molecular weight Bax oligomers/complexes on gel filtration. Bax oligomerization appears to be required for its proapoptotic activity, and the Bax oligomer/complex might constitute the structural entirety of the cytochromec-conducting channel in the outer mitochondrial membrane.

Mitochondrial Disease

2021 ◽  
pp. 1126-1133
Author(s):  
Radhika Dhamija ◽  
Erin Conboy ◽  
Ralitza H. Gavrilova
Keyword(s):  
Oxidative Phosphorylation ◽  
Mitochondrial Membrane ◽  
Protein Complexes ◽  
Mitochondrial Diseases ◽  
Mendelian Inheritance ◽  
Inner Mitochondrial Membrane ◽  
Oxidative Phosphorylation System ◽  
Transport Chain ◽  
Membrane Bound ◽  
Multimeric Protein

Primary mitochondrial diseases are a heterogeneous group of disorders that result from defects of the oxidative phosphorylation system of the mitochondria. Often underrecognized, mitochondrial diseases are uncommon (estimated incidence, 1 in 10,000 live births). Mitochondria are double-membrane–bound cytoplasmic organelles whose primary function is to provide energy (ie, adenosine triphosphate [ATP]) from the breakdown of carbohydrates, protein, and lipids by means of the electron transport chain and the oxidative phosphorylation system. The respiratory chain of mitochondria, located in the inner mitochondrial membrane, consists of 5 multimeric protein complexes (complexes I-IV and ATP synthase [complex V]). The structural proteins of these complexes are encoded by both mitochondrial and nuclear genes. Therefore, primary mitochondrial disorders can follow a maternal or mendelian inheritance pattern.

scholarly journals AAA Proteases: Guardians of Mitochondrial Function and Homeostasis

Cells ◽  
2018 ◽  
Vol 7 (10) ◽  
pp. 163 ◽  
Author(s):  
Magdalena Opalińska ◽  
Hanna Jańska
Keyword(s):  
Adenosine Triphosphate ◽  
Mitochondrial Function ◽  
Mitochondrial Membrane ◽  
Current Knowledge ◽  
Fine Tuning ◽  
Eukaryotic Cells ◽  
Mitochondrial Activity ◽  
Inner Mitochondrial Membrane ◽  
Membrane Bound ◽  
Aaa Atpases

Mitochondria are dynamic, semi-autonomous organelles that execute numerous life-sustaining tasks in eukaryotic cells. Functioning of mitochondria depends on the adequate action of versatile proteinaceous machineries. Fine-tuning of mitochondrial activity in response to cellular needs involves continuous remodeling of organellar proteome. This process not only includes modulation of various biogenetic pathways, but also the removal of superfluous proteins by adenosine triphosphate (ATP)-driven proteolytic machineries. Accordingly, all mitochondrial sub-compartments are under persistent surveillance of ATP-dependent proteases. Particularly important are highly conserved two inner mitochondrial membrane-bound metalloproteases known as m-AAA and i-AAA (ATPases associated with diverse cellular activities), whose mis-functioning may lead to impaired organellar function and consequently to development of severe diseases. Herein, we discuss the current knowledge of yeast, mammalian, and plant AAA proteases and their implications in mitochondrial function and homeostasis maintenance.

Primary and Secondary Carnitine Deficiency Syndromes

1995 ◽  
Vol 10 (2_suppl) ◽  
pp. 2S8-2S24 ◽  
Author(s):  
Roser Pons ◽  
Darryl C. De Vivo
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Mitochondrial Membrane ◽  
Carnitine Deficiency ◽  
Carnitine Palmitoyltransferase ◽  
Acid Oxidation ◽  
Inner Mitochondrial Membrane ◽  
Chain Acyl ◽  
Membrane Bound ◽  
Long Chain

The objective of this article is to review primary and secondary causes of carnitine deficiency, emphasizing recent advances in our knowledge of fatty acid oxidation. It is now understood that the cellular metabolism of fatty acids requires the cytosolic carnitine cycle and the mitochondrial β-oxidation cycle. Carnitine is central to the translocation of the long chain acyl-CoAs across the inner mitochondrial membrane. The mitochondrial β-oxidation cycle is composed of a newly described membrane-bound system and the classic matrix compartment system. Very long chain acyl-CoA dehydrogenase and the trifunctional enzyme complex are embedded in the inner mitochondrial membrane, and metabolize the long chain acyl-CoAs. The chain shortened acyl-CoAs are further degraded by the well-known system in the mitochondrial matrix. Numerous metabolic errors have been described in the two cycles of fatty acid oxidation; all are transmitted as autosomal recessive traits. Primary or secondary carnitine deficiency is present in all these clinical conditions except carnitine palmitoyltransferase type I and the classic adult form of carnitine palmitoyltransferase type II deficiency. The sole example of primary carnitine deficiency is the genetic defect involving the active transport across the plasmalemmal membrane. This condition responds dramatically to oral carnitine therapy. The secondary carnitine deficiencies respond less obviously to carnitine replacement. These conditions are managed by high carbohydrate, low fat frequent feedings, and vitamin/cofactor supplementation (eg, carnitine, glycine, and riboflavin). Medium chain triglycerides may be useful in the dietary management of patients with inborn errors of the cytosolic carnitine cycle or the mitochondrial membrane-bound long chain specific β-oxidation system. (J Child Neurol 1995;10(Suppl):2S8-2S24).

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