Human Molecular Genetics, Vol 5, 1643-1648, Copyright © 1996 by Oxford University Press
MM Lanterman, JR Dickinson and DJ Danner
Dihydrolipoamide dehydrogenase is a common component of mammalian
multienzyme complexes that decarboxylate alpha-ketoacids and catabolize
glycine. The common function is to reoxidize a reduced lipoate component of
each complex, thereby preparing that lipoate for another round of
catalysis. Regions within dihydrolipoamide dehydrogenase involved in
association with other proteins of the complexes are poorly defined, and
despite high amino acid sequence conservation through evolution, it is
unknown if dihydrolipoamide dehydrogenases are functionally equivalent
across species. To address this issue, we asked whether the human enzyme
could restore function to the alpha-ketoacid dehydrogenase complexes in a
yeast strain deficient in endogenous dihydrolipoamide dehydrogenase. This
dihydrolipoamide dehydrogenase null mutant will not grow on non-fermentable
carbon sources. The human enzyme expressed from a CEN plasmid complemented
the growth phenotype and restored full activity to the pyruvate and
alpha-ketoglutarate dehydrogenase complexes. Human dihydrolipoamide
dehydrogenases with selected amino acid substitutions were then tested in
the null strain for their ability to restore function. Substitutions tested
represented naturally occurring candidate mutations identified in an
individual with inactive dihydrolipoamide dehydrogenase. A K37E change had
full function while a P453L change resulted in reduced dihydrolipoamide
dehydrogenase abundance in the mitochondria and no detectable catalytic
activity.
ARTICLES
Functional analysis in Saccharomyces cerevisiae of naturally occurring amino acid substitutions in human dihydrolipoamide dehydrogenase
Department of Genetics and Molecular Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
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