A novel mutation in the ferrochelatase gene associated with erythropoietic protoporphyria.
Erythropoietic protoporphyria (EPP) is a hereditary disorder caused by mutations of the ferrochelatase gene. We investigated a Japanese patient with a dominant form of erythropoietic protoporphyria for a ferrochelatase mutation. Sequence analysis of the proband's ferrochelatase cDNA revealed a T to C point mutation at nucleotide 557. This mutation resulted in the replacement of Ile by Thr at amino acid position 186, a novel mutation in erythropoietic protoporphyria. An increase in ferrochelatase activity was not observed in the crude extract of E. coli over-expressing the mutant protein compared with the control, whereas a marked increase in activity was observed in that over-expressing the wild type. Prediction of the secondary structure of ferrochelatase suggested that the Ile186-->Thr mutation changed the original beta-sheet structure to an alpha helix in the region including amino acid residue of mutation. We conclude that, in the patient, the Ile186-->Thr mutation had abolished enzyme activity, possibly by disrupting the secondary structure, thereby causing erythropoietic protoporphyria.
Imoto
S
S
Third Department of Internal Medicine, Yamaguchi University School of Medicine, Japan.
Tanizawa
Y
Y
Sato
Y
Y
Kaku
K
K
Oka
Y
Y
D000328:Adult; D001483:Base Sequence; D015153:Blotting, Western; D005294:Ferrochelatase / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D017121:Porphyria, Hepatoerythropoietic / Q000235:genetics*
D005294:Ferrochelatase