PROTEIN AS A TRANSPORT TOOL

          Protein is the main component in living cells that play an important role in the life process. Protein plays a role in the structure and function of all living cells and viruses. protein allies in the form of enzymes as catalysts in a variety of biochemical processes. As a means of transport, ie hemoglobin protein binds and transports oxygen in the form of (Hb-O) to all parts of the body.

Protein also serves as a protector, as the antibodies if your body is possessed by foreign substances, as well as the control system in the form of hormones,

Protein is a very important component of protoplasm addition to the water. The role of proteins in cells, among others: 1. As a catalyst for many chemical reactions contained in the cell, namely as components in the enzyme. 2. Giving cell structural strength, namely tubulin, actin and myosin are involved in the formation of sitoskelet. 3. Monitoring the permeability of the membrane, the proteins that make up the cell membrane 4. Cause movement that occurs in sel5. Monitor the activities of the cell 6. Set the required levels of metabolites One of the functions of proteins are proteins as a means of transportation.

Transport Proteins: Hemoglobin and heme MioglobinProtein found in hemoglobin and myoglobin function in binding oxygen, oxygen transport and photosynthesis.

Figure 3. Oxygen binding curve of hemoglobin and myoglobin

Hemoglobin also transports H and CO2

In addition to carrying oxygen from the lungs to the tissues, hemoglobin also carries H and CO2 from the tissues to the lungs and kidneys for excreted. In the cell, organic fuel is oxidized by mitochondria to form CO2, water and other substances. Formation of CO2 increase in the tissue levels of H because hydration of CO2 produces H2CO3, a weak acid that dissociates to form H and HCO3-.

Hemoglobin   

 

Hemoglobin is metaloprotein (iron-containing protein) in red blood cells that serves as a carrier of oxygen from the lungs throughout the body in mammals and other animals. Hemoglobin is also the bearer of carbon dioxide back to the lungs to the body exhaled. Hemoglobin molecule consists of globin, Apoprotein, and four heme groups, an organic molecule with an iron atom. Mutations in these genes lead to a class of proteins hemoglobin decreased disease called hemoglobinopathy, among which the most common is sickle cell anemia and thalassemia. The structure of the central heterocyclic ring molecules are known to hold one atom porphyrin iron, the iron atom is a site / shop oxygen bond. Porphyrin-containing iron called heme. Hemoglobin name is a combination of heme and globin; globin as a generic term for globular proteins. There are several proteins containing heme and hemoglobin is the best known and most widely studied.

Cluster heme

In adult humans, hemoglobin tetramer form (containing 4 subunit proteins), consisting of each of the two alpha and beta subunits bound nonkovalen. Subunit-subunitnya structurally similar and similarly sized. Each subunit has a molecular weight of approximately 16.000 Dalton, so the total molecular weight tetramernya to about 64.000 Dalton. Each subunit contains a heme hemoglobin, so the overall hemoglobin has a capacity of four oxygen molecules: In the center there is a heterocyclic ring molecule known as porphyrin hold one atom of iron, the iron atom is a site / shop oxygen bond. Porphyrin called heme iron-containing hemoglobin Each subunit contains a heme, so overall hemoglobin has a capacity of four oxygen molecules. In the iron heme molecule is attached and delivers oxygen and carbon dioxide through the blood, these substances also makes our blood red.

 Reaction stages:

• Hb + O₂ <-> HbO₂
• HbO₂ + O₂ <-> Hb(O₂)₂
• Hb(O₂)₂ + O₂ <-> Hb(O₂)₃
• Hb(O₂)₃ + O₂ <-> Hb(O₂)₄

Overall reaction:

·         Hb + 4O₂ -> Hb(O₂)₄

Currently, measurement of hemoglobin levels in the blood have been using automatic machines. In addition to measuring hemoglobin, this machine can also measure some other blood components. Measurement machine will break down hemoglobin into a solution. Hemoglobin in solution is then separated from other substances by using a chemical called cyanide. Furthermore, the specific irradiation, hemoglobin levels were measured based on the value of successful light absorbed by hemoglobin What does it mean when the low hemoglobin levels? Hemoglobin concentration in the blood is low known as anemia. There are many causes of anemia among the most frequent are bleeding, malnutrition, bone marrow disorders, chemotherapy and congenital abnormalities of hemoglobin. What does it mean when a high hemoglobin levels high hemoglobin levels can be found in people who live in the highlands and smokers. Some diseases such as pneumonia, tumors and bone marrow disorders can also increase the levels of hemoglobin.

Myoglobin

Myoglobin (BM 16 700, abbreviated Mb) is an oxygen-binding protein that is relatively simple, it is found in large concentrations in bone and heart muscle, making it red tissue that serves as a store of oxygen and as a carrier of oxygen increases the rate of oxygen transport in muscle cells. Diving mammals such as whales dive for a long time, has a high concentration of myoglobin in the muscles. Proteins such as myoglobin are also commonly found in single-cell organisms. Myoglobin is a single polypeptide with 153 amino acid residues and the heme molecule. Component of myoglobin protein called globin, a single polypeptide chain containing eight α-helices (Fig. 1). Approximately 78% of the amino acid residues of the proteins found in the α-helix is.

Globin chain folds to form a gap that almost filled the heme group. Free heme [Fe 2] has a high affinity for O2 and unidirectional oxidized form hematin [Fe3]. Hematin can not bind O2. Nonkovalen interactions between amino acid side chain and the porphyrin ring containing nonpolar side slit tissue oxygen increases heme affinity for O2. Increased affinity Fe2 protect from oxidation and allows the reversible oxygen binding. All the amino acids that interact with nonpolar except two histidine heme, which binds directly to the heme iron atom and the other histidine stabilizes the tissue of oxygen. When the oxygen bound to the heme-free, position the axis of molecular oxygen on Fe-O bond angle (Fig. 2a), in contrast to this, when CO2 binds to free heme Fe, C and O are on a straight line (Fig. 2b). Both cases reflect the geometry of the orbital hybridization of each ligand. In myoglobin, His64 (His E7), at the O2 bind heme, too far away to coordinate with the heme iron, but interacting with a ligand bound to the heme. These residues are called distal his, which did not affect the binding of oxygen (Fig. 2c) but may block the binding of linear CO, explaining the reduction of CO binding to heme.

Oxygen fixation

 protein is a constituent of the blood that is myoglobin oxygen binding. Myoglobin unsuitable as an oxygen-carrying protein, but it is effective as an oxygen storage protein. Myoglobin in red muscle tissue that binds oxygen in a state of lack of oxygen to be released so that it can be used by the mitochondria of muscle for oxygen-dependent ATP synthesis. Oxygenated myoglobin, the oxygen molekulo sixth coordination position of the iron atom and the movement of His F8 and residue that covalently binds to the His F8 ring plane. This movement raises a new conformation for the parts of the protein.  

When O2 binds to myoglobin, the bond between an oxygen molecule with Fe2 is perpendicular to the plane of the heme. The second O2 molecule binds to 121o angle to the plane of the heme and directed away from the distal histidine. Pengikiatan oxygen bond breaking accompanied by anatar salt residue on a whole subunit carboxyl terminal. Binding of O2 further simplified because the number of bonds broken salt becomes less. These changes affect the structure of hemoglobin. One pair of sub-units α / α hold the rotation of the partner / other, so menempatlkan tentramer and enhance heme affinity for O2. When oxygenation, deoksihemoglobin iron atom moves into the heme ring plane. This movement is transmitted to the proximal histidine, which is moving toward the field and in the ring and the amino acid residue attached to his F8. The oxygen has been released from hemoglobin into the tissues, hemoglobin then mengamgkut CO2 and protons into the lungs. Excessive myoglobin can cause damage to the kidneys and eventually cause kidney failure.

Seruloplasmin

Seruloplasmin is an enzyme with copper substance that serves as a catalyst in organic reactions

 

 

4 Fe²⁺ + 4 H⁺ + O₂ <=> 4 Fe³⁺ + 2 H₂O

Ceruloplasmin activity of the enzyme has ferrioxidase that converts ferrous iron in the form of the cells and in the form of store with transferrin and ultimately used by the bone marrow to the manufacturing process of erythrocytes. Ceruloplasmin is the main form of copper minerals are present in the circulation of the blood (plasma). Forms of Cu in the body bind to a protein complex that is 90% bound to globulin in the form of ceruloplasmin and 10% by albumin. Ceruloplasmin have activity as an enzyme capable of converting ferroksidase iron in the ferrous form of the cells and in the form of store with transferring and ultimately used by the bone marrow to the process of making erythrocytes (erytropoiesis). Ceruloplasmin is α-2-globulin. This protein is blue because it contains copper and carry 90% of copper present in the plasma. Myoglobin myoglobin is a protein that is a constituent of the blood that binds oxygen. Myoglobin unsuitable as an oxygen-carrying protein, but it is effective as an oxygen storage protein. Myoglobin in red muscle tissue that binds oxygen in a state of lack of oxygen to be released so that it can be used by the muscle mitochondria for ATP synthesis are dependent on oxygen.