PROTEINS AS A TRANSPORT TOOL

Proteins are complex organic compounds of high molecular weight which are polymers of amino acid monomers are connected to each other by peptide bonds. Protein molecules containing carbon, hydrogen, oxygen, nitrogen and sometimes sulfur and phosphorus. Protein plays an important role in the structure and function of all living cells and viruses.

Its function is primarily protein is a cell structure forming elements, such as the hair, wool, kolgen, connective tissue, cell membranes, and others. Moreover, it can also function as an active proteins, such as enzymes, which act as catalysts in biochemical prses all cells. Protein enzymes are active besides hormones, hemoglobin, a protein that bound to the gene, tioksin, antibody / antigen and others.

Some characteristics of protein molecules is:
1. large molecular weight, thousands to millions, so it is a macromolecule.
2. generally consists of 20 different amino acids. Amino acid binding (covalently) to one another in the sequence variations are manifold, forming a polypeptide chain. Peptide bond is a bond between the α-carboxyl group of one amino acid with the α-amino group of another amino acid.
3. presence of other chemical bonds, leading to the formation of the arches of the polypeptide chain into three-dimensional structures of proteins. For instance, hydrogen bonding, hydrophobic bonds (bonds apolar), ionic bonds or electrostatic and van der Waals bonding.
4. The structure is not stable on several factors such as pH, radiation, temperature, medium organic solvents, and detergents.
5. umumya reactive and highly specific, due to the presence of a reactive side groups and a unique arrangement makromolekulnya structure.

Various kinds of side groups is that of a cation, anion, hydroxyl aromatic, aliphatic hydroxyl, amines, amides, thiols and heterocyclic group.

The classification is based on the biochemistry of proteins in biological function.
1. Enzyme
An enzyme is a protein group of the largest and most important. Examples of enzymes: ribonuklese, an enzyme that catalyzes the hydrolysis of RNA; cytochrome, involved in the process of moving electrons; tipsin, kataliator breaker certain peptide bonds in the polypeptide.

2. Protein Builders
Proteins serve as the building blocks of the structure. Some examples: wrapping viral protein, an envelope on the chromosome; glycoprotein, is supporting structure of the cell wall;

3. Protein Kontaktil
Is a class of proteins that play a role in the process of motion. For instance: myosin, filaments immobile element in the myofibrils; actin, filament elements engaged in myofibrils; dienin, shakes and hair found in the flagellum.

4. Protein Carrier
Has the ability to bind to specific molecules and transporting various substances through the blood stream. For example: hemoglobin, consisting of clusters of iron-containing compounds hame bound globin protein, functions as a carrier of oxygen in the blood of vertebrates; hemosianin, as an oxygen carrier in the blood of some kinds of invertebrates; serum albumin, fatty acid transporters in the blood; ceruloplasmin, copper ion transporters in the blood.

5. Protein Hormones
Some protein hormones are: insulin, glycated regulate metabolism; adrenokortikotrop, regulate the synthesis of corticosteroids; growth hormone, stimulates bone growth.

6. Equity Protein Toxins
Are toxic to animals high class: toxin of Clostridium botulinum, which causes food poisoning.

7. Protective Protein
Generally found in the blood of vertebrates. eg, antibodies, proteins formed if the antigen and the antigen is a foreign protein, can form complex compounds.

8. Protein Reserves
Saved for a variety of metabolic processes in the body. For example: ovalbumin, a protein contained padaputih eggs; zein, a protein in corn grain.

HEMOGLOBIN
Hemoglobin consists mostly of protein subunits, in turn, a large number of folded chains of amino acids called polypeptides different. Amino acid sequence of the polypeptide made by each cell, in turn determined by the stretch of DNA called genes. In all proteins, it is the sequence of amino acids that determine the nature and function of protein chemistry.


There is more than one hemoglobin gene. Amino acid sequence of the globin protein in hemoglobin usually differ between species. This difference grows with the evolutionary distance between species. For example, the most common hemoglobin sequences in humans and chimpanzees are nearly identical, differ by only one amino acid in both alpha and beta globin protein chains. This difference grows greater between species that are less closely related.

Even within a species, different variants of hemoglobin always exist, although one sequence is usually the "most common" one in each species. Mutations in the gene for hemoglobin protein in a species result in hemoglobin variants. Many mutant forms of hemoglobin cause no disease. Several mutant forms of hemoglobin, however, led to a group of hereditary diseases called hemoglobinopathies. The most famous hemoglobinopathy is sickle cell disease, which is the first human disease whose mechanism is understood at the molecular level. A set of (mostly) separate from a disease called thalassemia involves low production of normal hemoglobin and normal sometimes, through problems and mutations in globin gene regulation. All of these diseases result in anemia.

Variations in hemoglobin amino acid sequence, like other proteins, may be adaptive. For example, recent studies have shown genetic variants in deer mice that help explain how deer mice that live in the mountains are able to survive in the thin air that accompanies high altitudes. A researcher from the University of Nebraska-Lincoln found mutations in four different genes that can explain the difference between deer mice that live in the grassland plains versus mountains. After examining wild mice captured from both highlands and lowlands, it was found that: the genes of the two strains are "virtually identical-except for those who manage their hemoglobin oxygen-carrying capacity." "The genetic difference enables highland mice to make more efficient use of their oxygen", since less available at higher altitudes, such as in the mountains. Mammoth hemoglobin showing mutations that allow for the delivery of oxygen at lower temperatures, thus enabling mammoths to migrate to higher latitudes during the Pleistocene.

Hemoglobin (Hb) is synthesized in a complex series of steps. Heme part is synthesized in a series of steps in the mitochondria and cytosol immature red blood cells, while the globin protein parts are synthesized by ribosomes in the cytosol. Production of Hb continues in the cell during the early development of the proerythroblast to reticulocytes in the bone marrow. At this point, the nucleus is lost in mammalian red blood cells, but not in birds and other species. Even after losing the nucleus in mammals, residual ribosomal RNA allows further synthesis of Hb until the reticulocyte loses RNA soon after entering the blood vessels (this hemoglobin-synthetic RNA in fact gives the reticulocyte reticulated appearance and name). Glycine is a precursor of porphyrins.Myoglobin


Found in the muscle tissue of vertebrates, including humans, giving the muscle tissue gray or dark red different. It is very similar to hemoglobin in structure and sequence, but not tetramer, but is monomer without cooperative binding. It is used to store oxygen rather than transport it.

Hemocyanin
The second most common oxygen-transporting protein found in nature, is found in the blood of many arthropods and molluscs. Uses copper prosthetic groups instead of iron heme groups and is blue when the oxygen.

Hemerythrin
Some marine invertebrates and a few species of annelid use of non-heme iron-containing protein to carry oxygen in their blood. Appears pink / purple when oxygen, clear when not.

Chlorocruorin
Found in many annelids, very similar to erythrocruorin, but the heme group is significantly different in structure. Appears green when deoxygenated and red when oxygen.

Vanabins
Also known as vanadium chromagens, they are found in the blood of sea squirts. No one ever thought to use the rare metal vanadium as a prosthetic group binds oxygen. However, although they do contain vanadium by preference, they apparently bind little oxygen, and thus have some other function, which has not been described (sea squirts also contain some hemoglobin). They can act as a poison.

Erythrocruorin
Found in annelids, including earthworms, it is a giant free-floating blood protein containing many dozens-perhaps hundreds-and-heme iron-bearing protein subunits bound together into a single protein complex with a molecular mass greater than 3.5 million daltons.


Pinnaglobin
Just look at the mollusc Pinna squamosa. Brown manganese porphyrin-based protein.

Leghemoglobin
In leguminous plants, such as alfalfa or soybeans, nitrogen-fixing bacteria in the roots are protected from oxygen by the heme iron-containing oxygen-binding protein. Specific enzyme protected is nitrogenase, which can reduce nitrogen gas in the presence of free oxygen.

Coboglobin
A synthetic cobalt-based porphyrin. Coboprotein color will appear when the oxygen, but yellow when in veins.

Use and Abuse Hemoglobin
In addition to oxygen transport, hemoglobin can bind and transport other molecules such as nitric oxide and carbon monoxide. Nitric oxide affects the blood vessel walls, causing them to relax. This in turn reduces blood pressure. Recent studies have shown that nitric oxide can bind to specific cysteine ​​residues in hemoglobin and also to iron in the heme group, as shown in 1buw PDB entries. Thus, hemoglobin contribute to the regulation of blood pressure by distributing nitric oxide by blood. Carbon monoxide, on the other hand, is a poisonous gas. It easily replaces oxygen in the heme group, as seen in PDB entry 2hco and many others, forming a stable complex that is difficult to remove. This abuse of the heme binding and transport blocks of normal oxygen, suffocating the surrounding cells.


Artificial Blood
Blood transfusions have saved countless lives. However, the need for matching blood type, short life of stored blood, and the possibility of contamination are major concerns. An understanding of the workings of hemoglobin, based on decades of research into the biochemical and crystallographic structure of many, has prompted a search for blood substitutes and artificial blood. The most obvious approach is to use pure hemoglobin solution to replace lost blood. The main challenge is to maintain the hemoglobin protein chains four together. In the absence of the protective casing of red blood cells, four chain goes downhill fast. To avoid this problem, a novel hemoglobin molecule has been designed in which two of the four chains are physically connected together, as shown in 1c7d PDB entries. In this structure, two additional glycine residues form a relationship between the two chains, preventing their separation in solution.