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J. Biol. Chem., Vol. 276, Issue 18, 15225-15231, May 4, 2001
From the Hereditary tyrosinemia type 1 (HT1) is an
autosomal recessive disease caused by a deficiency of the enzyme
involved in the last step of tyrosine degradation, fumarylacetoacetate
hydrolase (FAH). Thus far, 34 mutations in the FAH gene have been
reported in various HT1 patients. Site-directed mutagenesis of the FAH cDNA was used to investigate the effects of eight missense
mutations found in HTI patients on the structure and activity of FAH.
Mutated FAH proteins were expressed in Escherichia coli and
in mammalian CV-1 cells. Mutations N16I, F62C, A134D, C193R, D233V, and
W234G lead to enzymatically inactive FAH proteins. Two mutations
(R341W, associated with the pseudo-deficiency phenotype, and Q279R)
produced proteins with a level of activity comparable to the wild-type enzyme. The N16I, F62C, C193R, and W234G variants were enriched in an
insoluble cellular fraction, suggesting that these amino acid
substitutions interfere with the proper folding of the enzyme. Based on
the tertiary structure of FAH, on circular dichroism data, and on
solubility measurements, we propose that the studied missense mutations
cause three types of structural effects on the enzyme: 1) gross
structural perturbations, 2) limited conformational changes in the
active site, and 3) conformational modifications with no significant
effect on enzymatic activity.
Copyright © 2001 by The American Society for Biochemistry and Molecular Biology, Inc. This article has been cited by other articles:
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