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Title: Structure of Human Ferritin L Chain

Abstract

Ferritin is the major iron-storage protein present in all cells. It generally contains 24 subunits, with different ratios of heavy chain (H) to light chain (L), in the shape of a hollow sphere hosting up to 4500 ferric Fe atoms inside. H-rich ferritins catalyze the oxidation of iron(II), while L-rich ferritins promote the nucleation and storage of iron(III). Several X-ray structures have been determined, including those of L-chain ferritins from horse spleen (HoSF), recombinant L-chain ferritins from horse (HoLF), mouse (MoLF) and bullfrog (BfLF) as well as recombinant human H-chain ferritin (HuHF). Here, structures have been determined of two crystal forms of recombinant human L-chain ferritin (HuLF) obtained from native and perdeuterated proteins. The structures show a cluster of acidic residues at the ferrihydrite nucleation site and at the iron channel along the threefold axis. An ordered Cd{sup 2+} structure is observed within the iron channel, offering further insight into the route and mechanism of iron transport into the capsid. The loop between helices D and E, which is disordered in many other L-chain structures, is clearly visible in these two structures. The crystals generated from perdeuterated HuLF will be used for neutron diffraction studies.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914142
Report Number(s):
BNL-78710-2007-JA
TRN: US0801571
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Cryst. D; Journal Volume: 62
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ATOMS; CHAINS; FERRITIN; HORSES; IRON; NEUTRON DIFFRACTION; NUCLEATION; OXIDATION; PROTEINS; RESIDUES; SHAPE; SPLEEN; STORAGE; TRANSPORT; NSLS; national synchrotron light source

Citation Formats

Wang,Z., Li, C., Ellenburg, M., Soistman, E., Ruble, J., Wright, B., Ho, J., and Carter, D. Structure of Human Ferritin L Chain. United States: N. p., 2006. Web. doi:10.1107/S0907444906018294.
Wang,Z., Li, C., Ellenburg, M., Soistman, E., Ruble, J., Wright, B., Ho, J., & Carter, D. Structure of Human Ferritin L Chain. United States. doi:10.1107/S0907444906018294.
Wang,Z., Li, C., Ellenburg, M., Soistman, E., Ruble, J., Wright, B., Ho, J., and Carter, D. Sun . "Structure of Human Ferritin L Chain". United States. doi:10.1107/S0907444906018294.
@article{osti_914142,
title = {Structure of Human Ferritin L Chain},
author = {Wang,Z. and Li, C. and Ellenburg, M. and Soistman, E. and Ruble, J. and Wright, B. and Ho, J. and Carter, D.},
abstractNote = {Ferritin is the major iron-storage protein present in all cells. It generally contains 24 subunits, with different ratios of heavy chain (H) to light chain (L), in the shape of a hollow sphere hosting up to 4500 ferric Fe atoms inside. H-rich ferritins catalyze the oxidation of iron(II), while L-rich ferritins promote the nucleation and storage of iron(III). Several X-ray structures have been determined, including those of L-chain ferritins from horse spleen (HoSF), recombinant L-chain ferritins from horse (HoLF), mouse (MoLF) and bullfrog (BfLF) as well as recombinant human H-chain ferritin (HuHF). Here, structures have been determined of two crystal forms of recombinant human L-chain ferritin (HuLF) obtained from native and perdeuterated proteins. The structures show a cluster of acidic residues at the ferrihydrite nucleation site and at the iron channel along the threefold axis. An ordered Cd{sup 2+} structure is observed within the iron channel, offering further insight into the route and mechanism of iron transport into the capsid. The loop between helices D and E, which is disordered in many other L-chain structures, is clearly visible in these two structures. The crystals generated from perdeuterated HuLF will be used for neutron diffraction studies.},
doi = {10.1107/S0907444906018294},
journal = {Acta Cryst. D},
number = ,
volume = 62,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The human ferritin L-chain cDNA was cloned into a vector for overproduction in Escherichia coli, under the regulation of a {lambda} promoter. The plasmid obtained contains the full L-chain coding region modified at the first two codons. It is able to direct the synthesis of the L-chain which can constitute up to 15% of the total soluble protein of bacterial extract. The L-chains assemble to form a ferritin homopolymer with electrophoretic mobility, molecular weight, thermal stability, spectroscopic, and immunological properties analogous to natural ferritin from human liver (95% L-chain). This recombinant L-ferritin is able to incorporate and retain iron inmore » solution at physiological pH values. At variance with the H-ferritin, the L form does not uptake iron at acidic pH values and does not show detectable ferroxidase activity. It is concluded that ferritin L-chain lacks the ferroxidase site present in the H-chain and that the two chains may have specialized functions in intracellular iron metabolism.« less
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  • Ferritin stores iron within a protein shell consisting of 24 subunits of two types, heavy (H) and light (L). According to Southern blotting, the rat genome contains four copies homologous to the H-subunit cDNA (H cDNA). To determine whether only one of these is expressed, H cDNAs isolated from rat liver and heart mRNAs were compared and found to share identical nucleotide sequences. Next, genomic clones for three of the four rat H-subunit loci were isolated. Two were classical processed pseudogenes, whereas the third contained an expressed gene. Comparison of the expressed rat H-subunit gene (H gene) structure with publishedmore » sequences for other species displays considerable conservation. The coding sequence of the rat H gene predicts 95% similarity to the human amino acid sequence, thus being more highly conserved than the L-subunit sequence of these species. Near the cap region of the 5' untranslated region, the rat H mRNA displays a 28-nucleotide sequence that is almost totally conserved in the corresponding region of the human, bullfrog, and chicken H mRNA and is also faithfully represented in the rat and human L-subunit mRNAs (L mRNAs), thus making this sequence a prime candidate for involvement in the known translational regulation of both subunits by iron. In the 5' flanking region, partially conserved sequences common to H gene and L-subunit gene (L gene) of the rat may be involved in transcriptional regulation by iron, whereas those conserved only in the H gene of man and the rat imply that other factors may independently control H-subunit regulation.« less
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