What is the difference between normal hemoglobin and sickle cell hemoglobin?

The main difference between normal hemoglobin and sickle cell hemoglobin is that normal hemoglobin contains glutamate at position 6 on the surface of the beta chain. But in sickle cell hemoglobin, valine replaces glutamate in the same place. In addition, glutamate in normal hemoglobin is highly hydrophilic, while valine makes sickle cell hemoglobin more hydrophobic. In addition, normal hemoglobin allows the red blood cells to have a biconcave shape to flow freely through the veins, while sickle cell hemoglobin causes the sickle cells to form a crescent shape and adhere to the branching points of the veins.  

Normal hemoglobin and sickle cell hemoglobin are two structural forms of hemoglobin, the iron-containing oxygen-transporting metalloprotein found in the red blood cells of almost all vertebrates. In general, hemoglobin A is the most common form of normal hemoglobin, while sickle cell hemoglobin is known as hemoglobin S.  

Key areas covered  

1. What is normal hemoglobin - definition, structure, meaning 2. What is sickle cell hemoglobin - definition, structure, meaning 3. What are the similarities between normal hemoglobin and sickle cell hemoglobin - overview of common features 4.What is the difference between Normal Hemoglobin and Sickle Cell Hemoglobin - Key Differences Comparison

key terms

Hemoglobin A, Hemoglobin S, Normal Hemoglobin, Sickle Cell Anemia, Sickle Cell Hemoglobin Difference Between Normal Hemoglobin and Sickle Cell Hemoglobin - Summary of Comparison

What is normal hemoglobin?  

Normal hemoglobin is usually found in vertebrate red blood cells. In particular hemoglobin A ( hemoglobin A1 or α 2 β 2 )   is the most common type of normal hemoglobin found in 95% of red blood cells. It is also a tetramer with two alpha subunits and two beta subunits (α 2 β 2 ). Aside from that, Hemoglobin A2 and Hemoglobin F are the other minor types of normal hemoglobin in adults.

Key difference - normal hemoglobin vs. sickle cell hemoglobin

Figure 1: Hemoglobin structure

In addition, hemoglobin is an iron-containing, oxygen-transporting metalloprotein in red blood cells. Since it is a collection of four globular proteins, each protein chain associates with a non-protein prosthesis   Hamm   Group. Usually the heme group consists of an iron (Fe) ion   in a heterocyclic. held   Ring known as porphyrin . The main function of hemoglobin is also to carry oxygen from the lungs around the body. It also transports carbon dioxide into the lungs.  

What is sickle cell hemoglobin ?  

Sickle cell hemoglobin is a variant of normal hemoglobin. The type of sickle cell hemoglobin is hemoglobin S, with a variation in the β chain gene that causes the properties of hemoglobin to change, resulting in sickling of red blood cells. Here sickle cell hemoglobin contains a single point mutation that ate substitute glutam   (E / Glu) from valine   (V / Val) at position 6 (E6V substitution). Usually glutamate is more hydrophilic while valine is more hydrophobic. This creates a new hydrophobic stain.

Difference Between Normal Hemoglobin and Sickle Cell Hemoglobin

Figure 2: Normal and sickle red blood cells

In addition, in the deoxygenated state, hydrophobic stains from both normal and sickle cell hemoglobin stick together and aggregate into chains. However, the amino acid composition in sickle cell hemoglobin is not exactly the same with respect to normal hemoglobin. Hence this aggregation differs in sickle cell hemoglobin. Valine also attaches to another hydrophobic patch in the beta chain. Ultimately, this results in the sickle cell hemoglobin tetramers adhering to each other, forming long fibers. Because of this, instead of remaining independent, it becomes polymerized. As a result, the polymerized sickle cell hemoglobin distorts the sickle red blood cells into an abnormal sickle shape.

It is important that the sickle-red blood cells tend to stick together at the branching points of the veins when the oxygen concentrations are low . Heterozygotes also have a mixture of hemoglobin A and hemoglobin S. Usually this condition is referred to as a "sickle cell trait". In contrast, the homozygous state leads to sickle cell anemia.  

Similarities Between Normal Hemoglobin and Sickle Cell Hemoglobin  

  • Normal hemoglobin and sickle cell hemoglobin are two structural forms of hemoglobin.  
  • Hemoglobin is generally the iron-containing metalloprotein found in the red blood cells of all vertebrates.  
  • It also has a quaternary structure made up of globular proteins with multiple subunits.  
  • Their function is to carry oxygen from the lungs to the rest of the body through the blood.  

Difference Between Normal Hemoglobin and Sickle Cell Hemoglobin  

definition  

Normal hemoglobin refers to the oxygen-carrying pigment in the blood, which is the predominant protein in red blood cells, while sickle cell hemoglobin refers to the most common form of abnormal hemoglobin and is the basis of both sickle cell anemia and sickle cell anemia.  

Type of hemoglobin  

The normal hemoglobin types include hemoglobin A, hemoglobin A2, and hemoglobin F in adults, while the sickle cell hemoglobin type is hemoglobin S.  

The difference in the content of amino acids  

Normal hemoglobin contains glutamate at position 6 on the surface of the beta chain, while in sickle cell hemoglobin valine replaces glutamate at the same position.  

Effect of the amino acid substitute  

Glutamate is highly hydrophilic in normal hemoglobin, while valine makes sickle cell hemoglobin more hydrophobic.  

Polymerization  

At low oxygen levels, normal hemoglobin is less likely to polymerize, while sickle cell hemoglobin tends to polymerize into crystals, causing red blood cells to distort into a sickle shape.  

The shape of the red blood cells  

Normal hemoglobin, red blood cells can form a biconcave accept, while sickle cell hemoglobin, red blood cells causes them to become crescent-shaped.  

Solubility at low oxygen concentrations  

Normal hemoglobin is more soluble at lower oxygen concentrations, while sickle cell hemoglobin is less soluble.  

Flow through veins  

Normal hemoglobin allows red blood cells to flow freely through the veins, while sickle cell hemoglobin causes sickle cells to become sticky at the branch points of the veins.  

effect  

Mutations in normal hemoglobin cause hemoglobinopathies and thalassemia, while sickle cell hemoglobin causes sickle cell anemia and sickle cell anemia.  

diploma  

Normal hemoglobin is the type of hemoglobin that is found in normal blood cells. In general, hemoglobin A is the most common form of normal hemoglobin in adults. In addition, normal hemoglobin does not undergo polymerization and allows normal red blood cells to maintain their biconcave structure. Therefore, when oxygen levels are low, normal red blood cells swim freely through the veins. In contrast, sickle cell hemoglobin is a mutation of normal hemoglobin, with valine replacing the glutamate at position 6 on the surface of the beta chain. As a result, the sickle cell hemoglobin becomes more hydrophobic, polymerizes the hemoglobin tetramers, and distorts the normal biconcave shape into a sickle shape. In addition, at low oxygen levels, this type of hemoglobin can become sticky at the branch points of the veins. Ultimately, sickle cell hemoglobin causes sickle cell anemia. Hence, the main difference between normal hemoglobin and sickle cell hemoglobin is structure and effect.  

References:

1. Driscoll, Timothy. "Sickle Hemoglobin." Hemoglobin Tutorial, Available Here . 2. “Hemoglobin S Molecule - What Causes Sickle Cell Anemia?” World of Molecules, available here.

Image courtesy:

1. "1904 Hemoglobin" from OpenStax College - Anatomy & Physiology, Connexions website. ( CC BY 3.0 ) via Commons Wikimedia 2. " Sickle Cell 01 " from the National Heart, Lung, and Blood Institute (NHLBI) (Public Domain) via Commons Wikimedia

About the author: Lakna

Lakna, a graduate in molecular biology and biochemistry, is a molecular biologist and has a broad and strong interest in discovering things related to nature