General Chemistry

Ferritin: The Iron-Storage Protein

How does the body regulate the amount of iron? Fortunately, most of us are able to maintain appropriate levels of available iron in the body (enough available iron to ensure an adequate supply of hemoglobin, but not so much as to produce toxic effects), even if our iron consumption does not always exactly match the body's iron loss. Ferritin (Figure 1) is the key to this important control of the amount of iron available to the body. Ferritin is a protein that stores iron and releases it in a controlled fashion. Hence, the body has a "buffer" against iron deficiency (if the blood has too little iron, ferritin can release more) and, to a lesser extent, iron overload (if the blood and tissues of the body have too much iron, ferritin can help to store the excess iron).

Iron stored as a mineral

Figure 1

This is a three-dimensional representation showing ferritin, the iron-storage protein in the body. Ferritin has a spherical shape, and iron (brown) is stored as a mineral inside the sphere.

Note: This same molecule is shown in another type of representation in Figure 9, below.

Note: The structure of this protein was determined using x-ray crystallography, the structure of the iron core is based on a simplified model compound, and the image was rendered using the Insight II molecular-modeling system from Molecular Simulations, Inc. (see References).

View Interactively
Note: To view this molecule interactively, please use Jmol, and click on the button to the left.

How does ferritin store iron? Ferritin has the shape of a hollow sphere. Inside the sphere, iron is stored in the Fe(III) oxidation state. It is incorporated in the mineral ferrihydrite, [FeO(OH)]8[FeO(H2PO4)], which is attached to the inner wall of the sphere. To release iron when the body needs it, the iron must be changed from the Fe(III) to the Fe(II) oxidation state. Then, the iron leaves through channels in the spherical structure. Thus, the structure of ferritin is extremely important for the protein's ability to store and release iron in a controlled fashion. In order to understand how ferritin helps to maintain the correct amount of available iron in the body, we must study the protein's structure in detail.

 


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This page created by Matt Traverso, Washington University in St Louis.
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Revised: 2004-08-08