The iron oxide core of the ferritin molecule

Haggis, G. H.

doi:10.1016/s0022-2836(65)80210-8

Cited by 90 publications

(40 citation statements)

References 8 publications

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“…A previous study of ferritin by dark-field high-voltage electron microscopy (16) already has indicated that the cores can have a substructure based upon their polycrystallinity. Crystallite sizes ranging from 40 to 75 iL have been estimated by x-ray and electron diffraction (9,10); these average figures fall within the even broader range of measurements of individual crystallites obtained in the present study. Fischbach and Anderegg (7), on the basis of their x-ray scattering curves, have postulated that the cores of fully saturated ferritin consist of a uniformly dense spherical particle about 73 A in diameter.…”

Section: Discussionsupporting

confidence: 82%

“…X-ray and electron diffraction of ferritin (9,10,23) has elicited polycrystalline ring patterns, thus indicating that some of the mineral forming the core is organized into the crystalline state. Diffraction patterns from ferritin cores do not correspond to the crystal structures of the well-known iron oxides in the natural world (9). Two models, based upon the diffraction data, have been proposed for the lattice structure of ferritin core crystallites.…”

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confidence: 99%

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The Ultrastructure of Ferritin Macromolecules. The Lattice Structure of the Core Crystallites

Massover

Cowley

1973

Proc. Natl. Acad. Sci. U.S.A.

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The ultrastructure of the crystalline ferric mineral that forms the central core of ferritin macromolecules has been examined by means of ultrahigh resolution electron microscopy at 100 kV. Very high magnification dark-field images reveal the presence of either a single large crystal or several smaller crystallites within many of the cores. When the highly crystalline core contents are suitably oriented to transmit their Bragg reflections through the objective aperture, regular fringes separated by 2-9.5 A have been visualized. The geometrical relations of lattice fringes and of periodically organized point details in these individual crystallites largely confirm the structural model proposed by Towe and Bradley (1967). The highly variable occupancy of ferric ions in certain planes of the lattice suggests that 20-33% of the iron content of fully saturated ferritin should undergo more rapid physiological release than does the remainder, and that iron uptake will have kinetics that depend upon more than only the maximal rate of crystallization.The variable iron content of the iron storage protein, ferritin, is present in a ferric mineral located within the central cavity of its apoprotein complex, apoferritin (5, 6). X-ray and electron diffraction of ferritin (9, 10, 23) has elicited polycrystalline ring patterns, thus indicating that some of the mineral forming the core is organized into the crystalline state. Diffraction patterns from ferritin cores do not correspond to the crystal structures of the well-known iron oxides in the natural world (9). Two models, based upon the diffraction data, have been proposed for the lattice structure of ferritin core crystallites. Harrison et al. (10) have concluded that these have a hexagonal unit cell with a = 2.94 A and c = 9.40 A. The best agreement of their postulated atomic positions with the actual diffraction patterns was achieved by proposing that the iron atoms are equally and randomly distributed among all of the available sites; both tetrahedral and octahedral coordination of the iron atoms with the oxygen groups was postulated. Towe and Bradley (23) have concluded that the ferritin core crystallites have a hexagonal unit cell with a = 5.08 A and c = 9.4 A. Their model proposes that occupancy by the iron atoms is optional in one of every four layers between the close-packed oxygen groups; in this model, only octahedral coordination was postulated. In addition to these two studies, Brady et al. (1) (Fig. 3). Spatial frequencies corresponding to real lattice periodicities of around 1-5 A were transmitted to the image plane (Fig. 3); the maximum arc of the diffraction rings being transmitted was near 800. The 3847

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Section: Discussionsupporting

confidence: 82%

mentioning

confidence: 99%

The Ultrastructure of Ferritin Macromolecules. The Lattice Structure of the Core Crystallites

Massover

Cowley

1973

Proc. Natl. Acad. Sci. U.S.A.

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“…phosphate "micelles" disposed in the center of the molecule (13,14); (c) it represents a particle population of remarkably uniform size; (d) it is a biological substance, a protein, similar in nature and comparable in size to most plasma proteins 2 ; (e) it is well tolerated by the experimental animals so that high concentrations can be achieved in the plasma without ill effects; (f) finally, it remains in high concentration in the circulating blood for at least 24 hr. Colloidal tracers (carbon, gold, mercuric sulfide) are less desirable because of their nonbiological nature and of the wide range of particle sizes.…”

Section: Methodsmentioning

confidence: 99%

Studies on Blood Capillaries

Bruns

Palade

1968

The Journal of Cell Biology

419

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The pathway by which intravenously injected ferritin molecules move from the blood plasma across the capillary wall has been investigated in the muscle of the rat diaphragm. At 2 min after administration, the ferritin molecules are evenly distributed in high concentration in the blood plasma of capillaries and occur within vesicles along the blood front of the endothelium. At the 10-min time point, a small number of molecules appear in the adventitia, and by 60 min they are relatively numerous in the adventitia and in phagocytic vesicles and vacuoles of adventitial macrophages. Thereafter, the amount of ferritin in the adventitia and pericapillary regions gradually increases so that at 1 day the concentration in the extracellular spaces approaches that in the blood plasma. Macrophages and, to a lesser extent, fibroblasts contain large amounts of ferritin. 4 days after administration, ferritin appears to be cleared from the blood and from the capillary walls, but it still persists in the adventitial macrophages and fibroblasts. At all time points examined, ferritin molecules within the endothelial tunic were restricted to vesicles or to occasional multivesicular or dense bodies; they were not found in intercellular junctions or within the cytoplasmic matrix. Ferritin molecules did not accumulate within or against the basement membranes. Over the time period studied, the concentration of ferritin in the blood decreased, first rapidly, then slowly, in two apparently exponential phases. Liver and spleen removed large amounts of ferritin from the blocd. Diaphragms fixed at time points from 10 min to 1 day, stained for iron by the Prussian Blue method, and prepared as cleared whole mounts, showed a progressive and even accumulation of ferritin in adventitial macrophages along the entire capillary network. These findings indicate: (1) that endothelial cell vesicles are the structural equivalent of the large pore system postulated in the pore theory of capillary permeability; (2) that the basement membrane is not a structural restraint in the movement of ferritin molecules across the capillary wall; (3) that transport of ferritin occurs uniformly along the entire length of the capillary; and (4) that the adventitial macrophages monitor the capillary filtrate and partially clear it of the tracer.

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“…7,24,[29][30][31] Haggis had previously reported in 1965 that a well-filled core could contain 5,000 iron atoms based on a core of FeOOH and a core diameter of 6.9 to 7.4 nm. 32 Fischbach and Anderegg, also in 1965, determined that an average of 4,300 iron atoms are contained in a "fully-filled" 418 kDa core with a diameter of 7.4 nm from sedimentation and small-angle X-ray scattering of HS-ApoFt and HS-HoloFt. 27,32 Salgado et al…”

Section: Introductionmentioning

confidence: 98%

Determination of Iron Content and Dispersity of Intact Ferritin by Superconducting Tunnel Junction Cryodetection Mass Spectrometry

et al. 2015

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Ferritin is a common iron storage protein complex found in both eukaryotic and prokaryotic organisms. Although horse spleen holoferritin (HS-HoloFt) has been widely studied, this is the first report of mass spectrometry (MS) analysis of the intact form, likely because of its high molecular weight ∼850 kDa and broad iron-core mass distribution. The 24-subunit ferritin heteropolymer protein shell consists of light (L) and heavy (H) subunits and a ferrihydrite-like iron core. The H/L heterogeneity ratio of the horse spleen apoferritin (HS-ApoFt) shell was found to be ∼1:10 by liquid chromatography-electrospray ionization mass spectrometry. Superconducting tunneling junction (STJ) cryodetection matrix-assisted laser desorption ionization time-of-flight MS was utilized to determine the masses of intact HS-ApoFt, HS-HoloFt, and the HS-HoloFt dimer to be ∼505 kDa, ∼835 kDa, and ∼1.63 MDa, respectively. The structural integrity of HS-HoloFt and the proposed mineral adducts found for both purified L and H subunits suggest a robust biomacromolecular complex that is internally stabilized by the iron-based core. However, cross-linking experiments of HS-HoloFt with glutaraldehyde, unexpectedly, showed the complete release of the iron-based core in a one-step process revealing a cross-linked HS-ApoFt with a narrow fwhm peak width of 31.4 kTh compared to 295 kTh for HS-HoloFt. The MS analysis of HS-HoloFt revealed a semiquantitative description of the iron content and core dispersity of 3400 ± 1600 (2σ) iron atoms. Commercially prepared HS-ApoFt was estimated to still contain an average of 240 iron atoms. These iron abundance and dispersity results suggest the use of STJ cryodetection MS for the clinical analysis of iron deficient/overload diseases.

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The iron oxide core of the ferritin molecule

Cited by 90 publications

References 8 publications

The Ultrastructure of Ferritin Macromolecules. The Lattice Structure of the Core Crystallites

The Ultrastructure of Ferritin Macromolecules. The Lattice Structure of the Core Crystallites

Studies on Blood Capillaries

Determination of Iron Content and Dispersity of Intact Ferritin by Superconducting Tunnel Junction Cryodetection Mass Spectrometry

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