Abstract
Eukaryotic cells contain highly homologous isozymes of malate dehydrogenase which catalyze the same reaction in different cellular compartments. To examine whether the metabolic functions of these isozymes are interchangeable, we have altered the cellular localization of mitochondrial malate dehydrogenase (MDH1) in yeast. Since a previous study showed that removal of the targeting presequence from MDH1 does not prevent mitochondrial import in vivo, we tested the role of a putative cryptic targeting sequence near the amine terminus of the mature polypeptide. Three residues in this region were changed to residues present in analogous positions in the other two yeast MDH isozymes. Alone, these replacements did not affect activity or localization of MDH1 but, in combination with deletion of the presequence, prevented mitochondrial import in vivo. Measurable levels of the resulting cytosolic form of MDH1 were low with expression from a centromere-based plasmid but were comparable to normal cellular levels with expression from a multicopy plasmid. The cytosolic form of MDH1 restored the ability of a ΔMDH1 disruption strain to grow on ethanol or acetate, suggesting that mitochondrial localization of MDH1 is not essential for its function in the TCA cycle. This TCA cycle function observed for the cytosolic form of MDH1 is unique to that isozyme since overexpression of MDH2 and of a cytosolic form of MDH3 in a ΔMDH1 strain failed to restore growth. Finally, only partial restoration of growth of a ΔMDH2 disruption mutant was attained with the cytosolic form of MDH1, suggesting that MDH2 may also have unique metabolic functions.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 53-60 |
| Number of pages | 8 |
| Journal | Archives of Biochemistry and Biophysics |
| Volume | 344 |
| Issue number | 1 |
| DOIs | |
| State | Published - Aug 1 1997 |
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ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology
Cite this
Metabolic effects of altering redundant targeting signals for yeast mitochondrial malate dehydrogenase. / Small, W. C.; McAlister-Henn, L.
In: Archives of Biochemistry and Biophysics, Vol. 344, No. 1, 01.08.1997, p. 53-60.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Metabolic effects of altering redundant targeting signals for yeast mitochondrial malate dehydrogenase
AU - Small, W. C.
AU - McAlister-Henn, L.
PY - 1997/8/1
Y1 - 1997/8/1
N2 - Eukaryotic cells contain highly homologous isozymes of malate dehydrogenase which catalyze the same reaction in different cellular compartments. To examine whether the metabolic functions of these isozymes are interchangeable, we have altered the cellular localization of mitochondrial malate dehydrogenase (MDH1) in yeast. Since a previous study showed that removal of the targeting presequence from MDH1 does not prevent mitochondrial import in vivo, we tested the role of a putative cryptic targeting sequence near the amine terminus of the mature polypeptide. Three residues in this region were changed to residues present in analogous positions in the other two yeast MDH isozymes. Alone, these replacements did not affect activity or localization of MDH1 but, in combination with deletion of the presequence, prevented mitochondrial import in vivo. Measurable levels of the resulting cytosolic form of MDH1 were low with expression from a centromere-based plasmid but were comparable to normal cellular levels with expression from a multicopy plasmid. The cytosolic form of MDH1 restored the ability of a ΔMDH1 disruption strain to grow on ethanol or acetate, suggesting that mitochondrial localization of MDH1 is not essential for its function in the TCA cycle. This TCA cycle function observed for the cytosolic form of MDH1 is unique to that isozyme since overexpression of MDH2 and of a cytosolic form of MDH3 in a ΔMDH1 strain failed to restore growth. Finally, only partial restoration of growth of a ΔMDH2 disruption mutant was attained with the cytosolic form of MDH1, suggesting that MDH2 may also have unique metabolic functions.
AB - Eukaryotic cells contain highly homologous isozymes of malate dehydrogenase which catalyze the same reaction in different cellular compartments. To examine whether the metabolic functions of these isozymes are interchangeable, we have altered the cellular localization of mitochondrial malate dehydrogenase (MDH1) in yeast. Since a previous study showed that removal of the targeting presequence from MDH1 does not prevent mitochondrial import in vivo, we tested the role of a putative cryptic targeting sequence near the amine terminus of the mature polypeptide. Three residues in this region were changed to residues present in analogous positions in the other two yeast MDH isozymes. Alone, these replacements did not affect activity or localization of MDH1 but, in combination with deletion of the presequence, prevented mitochondrial import in vivo. Measurable levels of the resulting cytosolic form of MDH1 were low with expression from a centromere-based plasmid but were comparable to normal cellular levels with expression from a multicopy plasmid. The cytosolic form of MDH1 restored the ability of a ΔMDH1 disruption strain to grow on ethanol or acetate, suggesting that mitochondrial localization of MDH1 is not essential for its function in the TCA cycle. This TCA cycle function observed for the cytosolic form of MDH1 is unique to that isozyme since overexpression of MDH2 and of a cytosolic form of MDH3 in a ΔMDH1 strain failed to restore growth. Finally, only partial restoration of growth of a ΔMDH2 disruption mutant was attained with the cytosolic form of MDH1, suggesting that MDH2 may also have unique metabolic functions.
UR - http://www.scopus.com/inward/record.url?scp=0031214131&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031214131&partnerID=8YFLogxK
U2 - 10.1006/abbi.1997.0179
DO - 10.1006/abbi.1997.0179
M3 - Article
C2 - 9244381
AN - SCOPUS:0031214131
VL - 344
SP - 53
EP - 60
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
SN - 0003-9861
IS - 1
ER -