Examination of Ferrochelatase Mutations That Cause Erythropoietic
Protoporphyria
V.M. Sellers,
T.A. Dailey, and
H.A. Dailey
From the Department of Microbiology, Department of Biochemistry and
Molecular Biology, and the Center for Metalloenzyme Studies, University
of Georgia, Athens, GA.
Ferrochelatase (E.C. 4.99.1.1), the enzyme that catalyzes the
terminal step in the heme biosynthetic pathway, is the site of defect
in the human inherited disease erythropoietic protoporphyria (EPP).
Previously it has been demonstrated that patients with EPP may have
missense mutations leading to amino acid substitutions, early chain
termination, or exon deletions. While it has been clearly demonstrated
that two missense mutations result in lowered enzyme activity, it has
never been shown what effect specific exon deletions may have. In the
current work, recombinant human ferrochelatase has been engineered to
have individual exon deletions corresponding to exons 3 through 11. When expressed in Escherichia coli, none of these possesses
significant enzyme activity and all lack the [2Fe-2S] cluster. One of
the human missense mutations, F417S, and a series of amino acid
replacements at this site (ie, F417W, F417Y, and F417L) were examined.
With the exception of F417L, all lacked enzyme activity and did not
contain the [2Fe-2S] cluster in vivo or as isolated in vitro.
Blood, Vol. 91 No. 10 (May 15), 1998:
pp. 3980-3985
© 1998 by The American Society of Hematology.
