Similarities: Hemoglobin (Hb) & Myoglobin (Mb)
Hemoglobin and Myoglobin are both members of the globin protein family. Their primary similarities are:
- Prosthetic Group: Both contain a Heme group (Iron-protoporphyrin IX) which serves as the site for oxygen binding.
- Oxidation State: In both proteins, the iron must be in the Ferrous state (Fe2+) to reversibly bind with molecular oxygen.
- Secondary Structure: Both are characterized by a high content of α-helices (roughly 70-80% of the polypeptide chain), which fold to create a hydrophobic pocket for the heme group.
- Folding Pattern: The 3D tertiary structure of Myoglobin is remarkably similar to the individual subunits (monomers) of the Hemoglobin tetramer.
- Ligand Specificity: Besides Oxygen (O2), both proteins have a much higher affinity for Carbon Monoxide (CO), which can lead to poisoning.
Chhatrapati Shahu Ji Maharaj University Kanpur (CSJMU) M.Sc. SEM – (III) 2018
Differences: Hemoglobin (Hb) vs. Myoglobin (Mb)
| Feature | Hemoglobin (Hb) | Myoglobin (Mb) |
|---|---|---|
| Structure | Tetramer (4 subunits) | Monomer (1 subunit) |
| Location | Red Blood Cells | Muscle Tissue |
| Function | Oxygen Transport | Oxygen Storage |
| Binding Curve | Sigmoidal (S-shaped) | Hyperbolic |
| Cooperativity | Yes (Positive Cooperativity) | No |