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Myoglobin Structure and Function

Myoglobin (Mb) is a structurally complex molecule that binds and stores oxygen inside of skeletal and cardiac muscles cells.

  • A large, coiled polypeptide called image descriptionglobin makes up most of the molecule.
Globin Molecule demonstrated in myoglobin
Globin Molecule Labeled demonstrated in myoglobin
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  • In a hydrophobic pocket formed by two of the globin’s folds is a image descriptionheme group. The heme consists of an atom of image descriptionferrous iron (Fe2+) and a surrounding image descriptionporphyrin ring (= four nitrogen-containing pyrrole molecules.
Globin Molecule demonstrated in myoglobin
Globin molecule with expanded view of heme group
Globin molecule and ferrous iron labeled demonstrated in myoglobin
Globin molecule and ferrous iron and polyphyrin ring labeled demonstrated in myoglobin
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  • The iron can reversibly image descriptionbond with one molecule of oxygen (O2).
Globin molecule and ferrous iron and polyphyrin ring labeled demonstrated in myoglobin
Binding to oxygen
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  • Two image descriptionhistidine molecules are associated with the heme. On one of the sides of the heme is the proximal histidine, which binds the Fe2+ of the heme to the nearby globin. It helps stabilize the position of the attached heme.
Binding to oxygen
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  • The distal histidine, which is not bound to the heme, helps prevent oxidation of Fe2+ to Fe3+. Oxygen does not bind to Fe3+.
  • The distal heme also reduces carbon monoxide’s (CO) affinity for heme, which makes it easier for O2 to bond.

An Overview of the Myoglobin Structure and Function:

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Test Yourself on Myoglobin with answers hidden
Test Yourself on Myoglobin with answers shown
Test yourself while observing Myoglobin Structure and Function
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