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Title
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Structural investigation of the complexation properties between horse spleen apoferritin and metalloporphyrins.
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Authors
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M.A.Michaux,
A.Dautant,
B.Gallois,
T.Granier,
B.L.d'Estaintot,
G.Précigoux.
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Ref.
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Proteins, 1996,
24,
314-321.
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PubMed id
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Abstract
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Crystallographic studies of L-chain horse spleen apoferritin (HSF)
co-crystallized with Pt-hematoporphyrin IX and Snprotoporphyrin IX have brought
significant new insights into structure-function relationships in ferritins.
Interactions of HSF with porphyrins are discussed. Structural results show that
the nestling properties into HSF are dependent on the porphyrin moiety. (Only
protoporphyrin IX significantly interacts with the protein, whereas
hematoporphyrin IX does not.) These studies additionally point out the L-chain
HSF ability to demetalate metalloporphyrins, a result which is of importance in
looking at the iron storage properties of ferritins. In both compound
investigated (whether the porphyrin reaches the binding site or not), the
complexation appears to be concomitant with the extraction of the metal from the
porphyrin. To analyze further the previous results, a three-dimensional
alignment of ferritin sequences based on available, crystallographic
coordinates, including the present structures, is given. It confirms a high
degree of homology between these members of the ferritin family and thus allows
us to emphasize observed structural differences: 1) unlike L-chain HSF, H-chain
human ferritin presents no preformed binding site; and 2) despite the absence of
axial ligands, and due to the demetalation, L-chain HSF is able to host
protoporphyrin at a similar location to that naturally found in bacterioferritin.
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