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PDBsum entry 1ld3
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Metal binding to bacillus subtilis ferrochelatase and interaction between metal sites.
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Authors
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D.Lecerof,
M.N.Fodje,
R.Alvarez león,
U.Olsson,
A.Hansson,
E.Sigfridsson,
U.Ryde,
M.Hansson,
S.Al-Karadaghi.
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Ref.
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J Biol Inorg Chem, 2003,
8,
452-458.
[DOI no: ]
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PubMed id
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Abstract
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Ferrochelatase, the terminal enzyme in heme biosynthesis, catalyses metal
insertion into protoporphyrin IX. The location of the metal binding site with
respect to the bound porphyrin substrate and the mode of metal binding are of
central importance for understanding the mechanism of porphyrin metallation. In
this work we demonstrate that Zn(2+), which is commonly used as substrate in
assays of the ferrochelatase reaction, and Cd(2+), an inhibitor of the enzyme,
bind to the invariant amino acids His183 and Glu264 and water molecules, all
located within the porphyrin binding cleft. On the other hand, Mg(2+), which has
been shown to bind close to the surface at 7 A from His183, was largely absent
from its site. Activity measurements demonstrate that Mg(2+) has a stimulatory
effect on the enzyme, lowering K(M) for Zn(2+) from 55 to 24 micro M. Changing
one of the Mg(2+) binding residues, Glu272, to serine abolishes the effect of
Mg(2+). It is proposed that prior to metal insertion the metal may form a
sitting-atop (SAT) complex with the invariant His-Glu couple and the porphyrin.
Metal binding to the Mg(2+) site may stimulate metal release from the protein
ligands and its insertion into the porphyrin.
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