Functional studies of mutations in the human protoporphyrinogen oxidase gene in variegate porphyria.
The autosomal dominant disorder, variegate porphyria (VP), results from mutations in the protoporphyrinogen oxidase (PPOX) gene. We have investigated the effects of 22 disease-associated missense mutations in this gene on enzyme activity. Mutants were generated in the expression plasmid pHPPOX by site-directed mutagenesis. They were screened for PPOX activity by complementation of the Escherischia coli strain SAS38X which lacks PPOX activity. Ten mutants (G40E, L85P, G232R, de1281H, V282D, L295P, V335G, S350P, L444P, G453V) had no detectable PPOX activity. PPOX activity of the remaining 12 mutants (L15F, R38P, L73P, V84G, D143V, R152C, L154P, V158M, R168H, A172V, V290L, G453R) ranged from less than 1% to 9.2% of wild-type activity. Our findings show that all 22 mutations substantially impair or abolish PPOX activity in a prokaryotic expression system and add to the evidence that they cause VP.
Morgan
Rhian R
RR
Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff, UK.
da
Silva Vasco
SV
Puy
Hervé
H
Deybach
Jean-Charles
JC
Elder
George H
GH
D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005420:Flavoproteins; D015870:Gene Expression / Q000235:genetics; D005816:Genetic Complementation Test; D006801:Humans; D024101:Mitochondrial Proteins; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors; D017094:Porphyrias, Hepatic / Q000201:enzymology / Q000235:genetics*; D050768:Protoporphyrinogen Oxidase
D005420:Flavoproteins; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C493978:PPOX protein, human; D050768:Protoporphyrinogen Oxidase