Metalloprotein

Metalloprotein is a generic term for a protein that contains a metal ion cofactor. A large number of all proteins are part of this category. It is estimated that approximately half of all proteins contain a metal. In another estimate, approximately one quarter to one third of all proteins are proposed to require metals to carry out their functions. Thus, metalloproteins have many different functions in cells, such as enzymes, transport and storage proteins, signal transduction proteins, and proteins involved in cell defense.

Structure

Metalloproteins have widely divergent structures and differing requirements for metal ions. Some proteins, such as ferritin, can have multiple metal ions within their structure. Ferritin is a protein that stores iron and releases it in a controlled fashion. The protein shell, or apoferritin, forms a cage to contain the iron. The type of iron protein complex is usually a function of the need of the organism. The iron storage protein of animals and many bacteria is ferritin. Some bacteria and fungi use another iron storage protein, bacterioferritin.

Function

Metalloproteins have many different functions in cells. For example, enzymes, transport and storage proteins, signal transduction proteins, and proteins involved in cell defense. They are involved in a wide range of biological processes, including electron transport, oxidation and reduction, and oxygen transport and reactive oxygen species production.

Examples

Some examples of metalloproteins include hemoglobin, cytochromes, and catalase. Hemoglobin contains iron, cytochromes contain heme iron, and catalase contains heme iron and also manganese in some organisms.

See also

• Metalloenzyme
• Metalloprotease
• Metalloproteinase
• Metallothionein

References

Metalloprotein Resources
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