Synthesis and Translocation of Mitochondrial Matrix Enzymes in Higher Animals with Special Reference to δ-Aminolevulinate Synthase

1982 ◽  
pp. 131-156 ◽  
Author(s):  
Goro Kikuchi ◽  
Norio Hayashi
Keyword(s):  
Special Reference ◽  
Mitochondrial Matrix ◽  
Aminolevulinate Synthase

The nine amino-terminal residues of delta-aminolevulinate synthase direct beta-galactosidase into the mitochondrial matrix

1986 ◽  
Vol 6 (2) ◽  
pp. 355-364
Author(s):  
T Keng ◽  
E Alani ◽  
L Guarente
Keyword(s):  
Amino Acid ◽  
Fusion Proteins ◽  
Specific Activity ◽  
Nuclear Gene ◽  
Yeast Cells ◽  
Mitochondrial Matrix ◽  
Aminolevulinate Synthase ◽  
Amino Terminal ◽  
Activity Measurements ◽  
Beta Galactosidase

delta-Aminolevulinate synthase, the first enzyme in the heme biosynthetic pathway, is encoded by the nuclear gene HEM1. The enzyme is synthesized as a precursor in the cytoplasm and imported into the matrix of the mitochondria, where it is processed to its mature form. Fusions of beta-galactosidase to various lengths of amino-terminal fragments of delta-aminolevulinate synthase were constructed and transformed into yeast cells. The subcellular location of the fusion proteins was determined by organelle fractionation. Fusion proteins were found to be associated with the mitochondria. Protease protection experiments involving the use of intact mitochondria or mitoplasts localized the fusion proteins to the mitochondrial matrix. This observation was confirmed by fractionation of the mitochondrial compartments and specific activity measurements of beta-galactosidase activity. The shortest fusion protein contains nine amino acid residues of delta-aminolevulinate synthase, indicating that nine amino-terminal residues are sufficient to localize beta-galactosidase to the mitochondrial matrix. The amino acid sequence deduced from the DNA sequence of HEM1 showed that the amino-terminal region of delta-aminolevulinate synthase was largely hydrophobic, with a few basic residues interspersed.

scholarly journals The nine amino-terminal residues of delta-aminolevulinate synthase direct beta-galactosidase into the mitochondrial matrix.

1986 ◽  
Vol 6 (2) ◽  
pp. 355-364 ◽  
Author(s):  
T Keng ◽  
E Alani ◽  
L Guarente
Keyword(s):  
Amino Acid ◽  
Fusion Proteins ◽  
Specific Activity ◽  
Nuclear Gene ◽  
Yeast Cells ◽  
Mitochondrial Matrix ◽  
Aminolevulinate Synthase ◽  
Amino Terminal ◽  
Activity Measurements ◽  
Beta Galactosidase

delta-Aminolevulinate synthase, the first enzyme in the heme biosynthetic pathway, is encoded by the nuclear gene HEM1. The enzyme is synthesized as a precursor in the cytoplasm and imported into the matrix of the mitochondria, where it is processed to its mature form. Fusions of beta-galactosidase to various lengths of amino-terminal fragments of delta-aminolevulinate synthase were constructed and transformed into yeast cells. The subcellular location of the fusion proteins was determined by organelle fractionation. Fusion proteins were found to be associated with the mitochondria. Protease protection experiments involving the use of intact mitochondria or mitoplasts localized the fusion proteins to the mitochondrial matrix. This observation was confirmed by fractionation of the mitochondrial compartments and specific activity measurements of beta-galactosidase activity. The shortest fusion protein contains nine amino acid residues of delta-aminolevulinate synthase, indicating that nine amino-terminal residues are sufficient to localize beta-galactosidase to the mitochondrial matrix. The amino acid sequence deduced from the DNA sequence of HEM1 showed that the amino-terminal region of delta-aminolevulinate synthase was largely hydrophobic, with a few basic residues interspersed.

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

1990 ◽  
Vol 48 (2) ◽  
pp. 166-167
Author(s):  
W.A. Jacob ◽  
R. Hertsens ◽  
A. Van Bogaert ◽  
M. De Smet
Keyword(s):  
Energy Metabolism ◽  
Calcium Ions ◽  
Energy Production ◽  
Regulation Of Respiration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Cytochemical Study ◽  
Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

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