scholarly journals Hydrophobic interaction between the monomer of mitochondrial malate dehydrogenase and phospholipid membranes

1980 ◽  
Vol 186 (1) ◽  
pp. 227-233 ◽  
Author(s):  
K A Webster ◽  
K B Freeman ◽  
S Ohki
Keyword(s):  
Malate Dehydrogenase ◽  
Conformational Changes ◽  
Ribonuclease A ◽  
Phospholipid Vesicles ◽  
Mitochondrial Matrix ◽  
Dimer Formation ◽  
Dimeric Form ◽  
Oil Water ◽  
Mitochondrial Malate Dehydrogenase

Porcine mitochondrial malate dehydrogenase (EC 1.1.1.37) dissociates into subunits on dilution. The enzyme monomer caused large increases in the surface pressure of monolayers of 1:1 phosphatidylserine/phosphatidylcholine at air/water and oil/water interfaces. The monomer increased the permeability of phospholipid vesicles to 22Na+. Both effects were significantly greater than the corresponding effects of ribonuclease A, cytochrome c and the dimeric form of malate dehydrogenase. Changes in the circular-dichroism spectra of the enzyme indicated that conformational changes may be associated with dimer formation or when monomer interacts with lysophosphatidyl-choline. Similar interactions to those described may occur in situ when mitochondrial malate dehydrogenase is transported to the mitochondrial matrix from its site of synthesis on cytosolic ribosomes.

scholarly journals Interaction of mitochondrial malate dehydrogenase monomer with phospholipid vesicles

1979 ◽  
Vol 178 (1) ◽  
pp. 147-158 ◽  
Author(s):  
K A Webster ◽  
H V Patel ◽  
K B Freeman ◽  
D Papahadjopoulos
Keyword(s):  
Conformational Change ◽  
Malate Dehydrogenase ◽  
Alpha Helix ◽  
Phospholipid Vesicles ◽  
Mitochondrial Matrix ◽  
Enzyme Subunits ◽  
Direct Binding ◽  
Mitochondrial Malate Dehydrogenase ◽  
Circular Dichroïsm ◽  
In Cells

The association between bovine and porcine mitochondrial malate dehydrogenase (EC 1.1.1.37) and phospholipid vesicles was investigated. At concentrations at which malate dehydrogenase exists as a dimer, entrapment within the aqueous compartment but not binding of the 14C-labelled enzyme was observed. The dissociated enzyme was labile to moderate heat and to p-chloromercuribenzoate, but in both cases inactivation was decreased by incubation with suspensions of charged phospholipid vesicles. This suggested an interaction between enzyme subunits and phospholipid, and this was confirmed by direct binding measurements and by studies that followed changes in the fluorescein-labelled enzyme. The circular-dichroism spectra of the enzyme indicated a high alpha-helix content, and suggested that a small conformational change occurred when the enzyme dissociated. Fluorescence data also suggested less-rigid molecules after dissociation. A possible mechanism, based on the flexibility of enzyme monomer and its interaction with phospholipids, by which mitochondrial matrix enzymes are specifically localized in cells, is discussed.

Krebs cycle metabolon formation: metabolite concentration gradient enhanced compartmentation of sequential enzymes

2015 ◽  
Vol 51 (7) ◽  
pp. 1244-1247 ◽  
Author(s):  
Fei Wu ◽  
Lindsey N. Pelster ◽  
Shelley D. Minteer
Keyword(s):  
Malate Dehydrogenase ◽  
Concentration Gradient ◽  
Citrate Synthase ◽  
Krebs Cycle ◽  
Microfluidic Channel ◽  
Metabolite Concentration ◽  
Concentration Region ◽  
Directional Diffusion ◽  
Mitochondrial Malate Dehydrogenase

The substrate (l-malate) gradient created in a microfluidic channel induced the directional diffusion of mitochondrial malate dehydrogenase (mMDH) toward a higher concentration region and in situ generation of an intermediate (OAA) gradient enhanced the co-diffusion of citrate synthase (CS) together with mMDH.

Translocation of precursor proteins into the mitochondrial matrix occurs through an environment accessible to aqueous perturbants

1989 ◽  
Vol 94 (4) ◽  
pp. 695-701 ◽  
Author(s):  
E.S. Sztul ◽  
T.W. Chu ◽  
A.W. Strauss ◽  
L.E. Rosenberg
Keyword(s):  
Malate Dehydrogenase ◽  
Integral Membrane Proteins ◽  
Leader Peptide ◽  
Mitochondrial Matrix ◽  
Mitochondrial Membranes ◽  
Precursor Proteins ◽  
Nonionic Detergent ◽  
Triton X ◽  
Polypeptide Chains ◽  
Mitochondrial Malate Dehydrogenase

We have identified translocational intermediates generated during import of precursor proteins into the mitochondrial matrix and have characterized their association with mitochondrial membranes. Partially translocated forms of mitochondrial malate dehydrogenase (MDH) and ornithine transcarbamylase (OTC) were generated during import of the corresponding precursors (pMDH and pOTC) into mitochondria at 2 degrees C. Import at this temperature results in the formation of intermediate-sized MDH (iMDH) and OTC (iOTC) produced by the removal of a portion of the leader peptide, and in the production of mature-sized MDH. All of these forms contain NH2 termini located within the mitochondrial matrix, although the majority of their polypeptide chains remain extramitochondrial. All three are strongly associated with mitochondrial membranes, but can be extracted by protein denaturants such as urea. These translocational intermediates appear to be hydrophilic proteins, on the basis of their partitioning properties during extraction with the nonionic detergent Triton X-114. The data indicate that the translocation of polypeptide chains into mitochondria occurs in a microenvironment that is aqueous in nature and is mediated by integral membrane proteins.

scholarly journals STUDIES ON THE CONFORMATIONAL CHANGES OF MITOCHONDRIAL MALATE DEHYDROGENASE IN UREA–PHOSPHATE SOLUTIONS

1967 ◽  
Vol 45 (5) ◽  
pp. 659-669 ◽  
Author(s):  
R. J. Seguin ◽  
G. W. Kosicki
Keyword(s):  
Malate Dehydrogenase ◽  
Conformational Changes ◽  
Inorganic Phosphate ◽  
Protein Molecule ◽  
Order Rate Constant ◽  
Sulfhydryl Groups ◽  
First Order ◽  
Phosphate Ions ◽  
Mitochondrial Malate Dehydrogenase ◽  
Phosphate Solutions

Pig-heart mitochondrial malate dehydrogenase is gradually inactivated in 4 M urea. During the inactivation, sulfhydryl groups on the protein are exposed in a first-order reaction. The reaction is followed spectrophotometricaily using the sulfhydryl reagent, 5,5′-dithiobis(2-nitrobenzoate) (DTNB). Titration with DTNB in the presence of urea exposes 10 to 12 sulfhydryl groups per molecule of mitochondrial malate dehydrogenase. The enzyme is also inactivated when diluted in water but no sulfhydryl groups are unmasked. The loss of activity and the appearance of sulfhydryl groups in urea solutions do not take place at the same rate.The conformational changes of malate dehydrogenase that occur in urea solutions are partially prevented by inorganic phosphate ions, and less so by the substrates NADH, NAD+, oxalacetate (OAA), and L-malate. The protection against loss of enzyme activity by inorganic phosphate ions is pH-dependent. Both inorganic phosphate and NADH considerably reduce the first-order rate constant for sulfhydryl appearance in 4 M urea. Protection of the enzyme against sulfhydryl appearance in urea solutions by pre-incubation with the substrates indicates that about two sulfhydryl groups per molecule of mitochondrial malate dehydrogenase are involved in substrate binding. Thus, the substrates must keep the active site of the enzyme intact. They either bind to the sulfhydryl groups or prevent the protein molecule from completely unfolding.

scholarly journals The Sorting of Mitochondrial DNA and Mitochondrial Proteins in Zygotes: Preferential Transmission of Mitochondrial DNA to the Medial Bud

1998 ◽  
Vol 142 (3) ◽  
pp. 613-623 ◽  
Author(s):  
Koji Okamoto ◽  
Philip S. Perlman ◽  
Ronald A. Butow
Keyword(s):  
Mitochondrial Dna ◽  
Fluorescent Protein ◽  
Yeast Cells ◽  
Mitochondrial Matrix ◽  
Outer Membranes ◽  
Marker Proteins ◽  
The Matrix ◽  
Green Fluorescent ◽  
Mitochondrial Reticulum

Green fluorescent protein (GFP) was used to tag proteins of the mitochondrial matrix, inner, and outer membranes to examine their sorting patterns relative to mtDNA in zygotes of synchronously mated yeast cells in ρ+ × ρ0 crosses. When transiently expressed in one of the haploid parents, each of the marker proteins distributes throughout the fused mitochondrial reticulum of the zygote before equilibration of mtDNA, although the membrane markers equilibrate slower than the matrix marker. A GFP-tagged form of Abf2p, a mtDNA binding protein required for faithful transmission of ρ+ mtDNA in vegetatively growing cells, colocalizes with mtDNA in situ. In zygotes of a ρ+ × ρ+ cross, in which there is little mixing of parental mtDNAs, Abf2p–GFP prelabeled in one parent rapidly equilibrates to most or all of the mtDNA, showing that the mtDNA compartment is accessible to exchange of proteins. In ρ+ × ρ0 crosses, mtDNA is preferentially transmitted to the medial diploid bud, whereas mitochondrial GFP marker proteins distribute throughout the zygote and the bud. In zygotes lacking Abf2p, mtDNA sorting is delayed and preferential sorting is reduced. These findings argue for the existence of a segregation apparatus that directs mtDNA to the emerging bud.

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