The N-Terminal Region of Mature Mitochondrial Aspartate Aminotransferase Can Direct Cytosolic Dihydrofolate Reductase into Mitochondria in Vitro

1994 ◽  
Vol 201 (3) ◽  
pp. 1059-1065 ◽  
Author(s):  
S. Giannattasio ◽  
A. Azzariti ◽  
E. Marra ◽  
E. Quagliariello
Keyword(s):  
Dihydrofolate Reductase ◽  
Aspartate Aminotransferase ◽  
Terminal Region ◽  
Mitochondrial Aspartate Aminotransferase

scholarly journals Kinetic studies of the uptake of aspartate aminotransferase and malate dehydrogenase into mitochondria in vitro

1985 ◽  
Vol 228 (2) ◽  
pp. 493-503 ◽  
Author(s):  
E Marra ◽  
S Passarella ◽  
E Casamassima ◽  
E Perlino ◽  
S Doonan ◽  
...  
Keyword(s):  
Malate Dehydrogenase ◽  
Binding Sites ◽  
Aspartate Aminotransferase ◽  
Kinetic Studies ◽  
Membrane System ◽  
Model System ◽  
Kinetic Measurements ◽  
Enzymes Inhibition ◽  
Mitochondrial Aspartate Aminotransferase

Kinetic measurements of the uptake of native mitochondrial aspartate aminotransferase and malate dehydrogenase into mitochondria in vitro were carried out. The uptake of both the enzymes is essentially complete in 1 min and shows saturation characteristics. The rate of uptake of aspartate aminotransferase into mitochondria is decreased by malate dehydrogenase, and vice versa. The inhibition is exerted by isoenzyme remaining outside the mitochondria rather than by isoenzyme that has been imported. The thiol compound beta-mercaptoethanol decreases the rate of uptake of the tested enzymes; inhibition is a result of interaction of beta-mercaptoethanol with the mitochondria and not with the enzymes themselves. The rate of uptake of aspartate aminotransferase is inhibited non-competitively by malate dehydrogenase, but competitively by beta-mercaptoethanol. The rate of uptake of malate dehydrogenase is inhibited non-competitively by aspartate aminotransferase and by beta-mercaptoethanol. beta-Mercaptoethanol prevents the inhibition of the rate of uptake of malate dehydrogenase by aspartate aminotransferase. These results are interpreted in terms of a model system in which the two isoenzymes have separate but interacting binding sites within a receptor in the mitochondrial membrane system.

scholarly journals Removal of an N-terminal peptide from mitochondrial aspartate aminotransferase abolishes its interactions with mitochondria in vitro

1985 ◽  
Vol 228 (3) ◽  
pp. 609-614 ◽  
Author(s):  
K M O'Donovan ◽  
S Doonan ◽  
E Marra ◽  
S Passarella ◽  
E Quagliariello
Keyword(s):  
Catalytic Activity ◽  
Rat Liver ◽  
Aspartate Aminotransferase ◽  
Terminal Segment ◽  
Model System ◽  
Native Enzyme ◽  
Cysteine Residues ◽  
Native Form ◽  
Mitochondrial Aspartate Aminotransferase

Treatment of mitochondrial aspartate aminotransferase from rat liver with trypsin leads to specific cleavage of the bonds between residues 26 and 27, and residues 31 and 32. The proteolysed enzyme has only a small residual catalytic activity, but retains a conformation similar to that of the native form as judged by accessibility and reactivity of cysteine residues. Proteolysis abolishes the ability of the enzyme either to bind to mitochondria or to be imported into the organelles. This suggests that the N-terminal segment of the native enzyme is essential for both of these functions, at least in the model system used to study the import process.

scholarly journals Selective permeability of rat liver mitochondria to purified aspartate aminotransferases in vitro

1977 ◽  
Vol 164 (3) ◽  
pp. 685-691 ◽  
Author(s):  
E Marra ◽  
S Doonan ◽  
C Saccone ◽  
E Quagliariello
Keyword(s):  
Rat Liver ◽  
Aspartate Aminotransferase ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Transferase Activity ◽  
Selective Permeability ◽  
The Matrix ◽  
Mitochondrial Aspartate Aminotransferase

1. A method was devised to allow determination of intramitochondrial aspartate amino-transferase activity in suspensions of intact mitochondria. 2. Addition of purified rat liver mitochondrial aspartate aminotransferase to suspensions of rat liver mitochondria caused an apparent increase in the intramitochondrial enzyme activity. No increase was observed when the mitochondria were preincubated with the purified cytoplasmic isoenzyme. 3. These results suggest that mitochondrial aspartate aminotransferase, but not the cytoplasmic isoenzyme, is able to pass from solution into the matrix of intact rat liver mitochondria in vitro. 4. This system may provide a model for studies of the little-understood processes by which cytoplasmically synthesized components are incorporated into mitochondria in vivo.

The in vitro-synthesized precursor and mature mitochondrial aspartate aminotransferase share the same import pathway in isolated mitochondria

1991 ◽  
Vol 290 (2) ◽  
pp. 528-534 ◽  
Author(s):  
Sergio Giannattasio ◽  
Ersilia Marra ◽  
Maria Filomena Abruzzese ◽  
Margherita Greco ◽  
Ernesto Quagliariello
Keyword(s):  
Aspartate Aminotransferase ◽  
Isolated Mitochondria ◽  
Mitochondrial Aspartate Aminotransferase
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