Proteins are the polymers of aminic acids. They are made up of a big figure of monomer units aminic acids. The amino acids are linked together by the peptide bonds in a protein.
The additive agreement of aminic acids forms the primary construction of a protein. This additive sequences of amino acids sometimes creases at certain points in the polypeptide by the formation of disulfide bonds and H bonds. The construction formed is called as secondary construction of proteins.
When the secondary construction further creases due to the hydrophobic interactions and some other forces like H bonds, it consequences in the formation of complex construction which is now referred to as third construction. The third construction is besides known as a three dimensional constructions of proteins. We can see that the sequence of aminic acids in the primary construction is responsible its concluding three dimensional construction.
The proteins execute different maps. Some act as bearer proteins ( eg. haemoglobin ) , some as storage proteins ( caesin ) and some as signaling proteins. The map of proteins besides depends on its construction. “ The protein do non work if they are denatured from its native construction ” ( Lehninger, 1995 ) .
So the amino acerb sequences of the polypeptide plays a critical function in finding the protein construction and eventually its maps.
A protein is a polymer that is made up of many polypeptide linked monomers called the amino acids. This concatenation is frequently referred to as polypeptide concatenation. The proteins are the complex constructions that under goes four degrees of organisations ; the primary constructions, secondary, third and quaternate constructions. The monomers or the aminic acids in a polypeptide are responsible for the construction of proteins. ( Griffiths, 2008 )
Different proteins have different constructions which determine their assorted maps in the life system. For illustration the construction of haemoglobin is different from the ceratin whereby they besides perform different maps. As mentioned earlier, the protein or the polypeptide concatenation is formed of many monomers known as amino acids. These aminic acids are arranged in a additive sequence linked each other by the peptide bonds. The additive sequence of aminic acids joined together by the peptides, forms the Primary construction of the proteins. ( David and Nigel, 2004 ) .
For illustration, the first 10 aminic acids of human adrinocorticotrophin out of 39 is given below:
Ser – Tyr – Ser – Met – Glu – His – Phe – Arg – Trp – Gly aˆ¦aˆ¦aˆ¦ . ( Lehninger 1995 )
When the anchor of polypeptide starts turn uping at some point, it forms a coiling construction which is normally called as the secondary construction of the proteins. There are two most common signifier of secondary constructions ; the I± spiral and the I? pleated sheets.
aˆ? The I± spiral.
Fig. 1 ( Beginning: Ophardt, 2003 )
In this construction the polypeptide incorporating sequence of aminic acids is wound in a coiling mode around the fanciful axis drawn through the coiling. In this construction the side ironss or the R groups of aminic acids are all positioned along the exterior of the cylindrical spiral. It has been found that there are 3.6 aminic acids per bend of the spiral and is 5.4 A ( Freifelder, 1986 ) long along the axis. Naturally happening L-amino acids can organize either right or left handed I± spirals.
In a polypeptide of amino acid sequence, the carbonyl O of one amino acid forms the H bond with the H atom attached to the negatively charged N atom of the 4th amino acid. Each consecutive bend of the spiral is held to the next bend by 3-4 H bonds ( Freifelder, 1986 ) which stabilize the construction.
aˆ? The I? pleated sheet.
The 2nd type of secondary construction is the I? conformation. Unlike the coiling construction the polypeptide concatenation is formed into zig-zag conformation. The zigzag polypeptide concatenation can set up side by side in the signifier of series of plaits and hence it is known as I? pleated sheet which are cross linked by interchain H bonds. ” The peptide linkage of the amino acid sequence besides take part in this cross associating and supply greater stableness ” ( Lehninger,1995 ) .
The H bond are formed between the next amino acid of a polypeptide. The side ironss of the next amino acid comes out from the zigzag construction in the opposite waies. The two sections of the polypeptide concatenation can organize two types of I? construction depending on the comparative orientation of the sections.
aˆ? Parallel I? pleated sheet.
If both the sections are aligned in the same way, either from N-C terminus or from C-N terminal way, it is said to be in parallel status.
aˆ? Anti analogue I? pleated sheet.
( Beginning: Chodges, 2006 )
If the two sections move in the opposite way, that is if one section is directed from N-C terminus and the other from C-N terminus, it is said to be in anti parallel signifier. ( David Freidler,1986 ) .
The 3rd degree of construction of protein is the third construction. The extended folding of anchor of polypeptide, where the amino acid that are far apart in the additive sequence and every bit good as those that are next are connected to organize a construction known as the three dimensional constructions. The third construction of protein is determined by its amino acid sequence. This was proved by the experiment, that the denaturation of some proteins are reversible through the procedure called renaturation.
“ For illustration the denaturation of ribonucleinase by exposure to concentrated urea solution in presence of cut downing agent loses its catalytic activity. The cut downing agent interrupt down the four disulfide bonds and the urea disrupts the stabilising hydrophobic interactions therefore blossoming the polypeptide. But it was found that when urea and cut downing agent are removed, the ribonucleinase refolds by organizing disulfide bonds and in the same place as that of its nstive construction ” . ( Nelson and Cox, 2003 ) . This shows that the 3D construction of ribonucleinase is due to the disulfides bonds formed by the cystein residues and hydrophobic interactions of the amino acerb sequence in a polypeptide concatenation. It was besides found out that the amino acerb sequence in a polypeptide concatenation contains all the information required for protein turn uping into its native construction. ( David and Michael, 2003 ) .
Some protein missing disulfide cross nexus can besides refold into its native construction after denaturation. Afinsen and his co-workers found out that the nuclease from staphylococci cells losingss its biological activities at pH-3 but when restored to pH-7, it regains its activities. This shows that the amino acerb sequence specifies the typical third construction. ( Lehninger,1995 ) .
The most of import interactions responsible for third constructions are:
aˆ? Ionic bonds between oppositely charged groups in acidic and basic amino acids.
aˆ? Hydrogen bonds.
aˆ? Hydrophobic interactions.
The disulfide bonds and hydrophobic interactions bring the distant amino acids together. Van der waals forces produce specific interactions between the bunchs of aminic acids in a polypeptide ( Freifelder,1986 ) . All these factors are responsible for stabilising the 3D construction of proteins.
A human being produces over 50000-100000 different proteins ( David and Michael, 2003 ) . Each protein has a alone 3D construction and the construction gives it a alone map. Each protein has alone amino acid sequence and its dramas a cardinal function in finding the 3D construction of protein and eventually it ‘s map.
It was clear from the above described experiment that when a protein is denatured by some denaturing agent, it loses its biological activity wholly, but regains its map on remotion of denaturing agents. This explains that the complex constructions are responsible for the map of the proteins.
For illustration the form of the enzymes is really specific to the form of its substrates. The form of the enzyme should suit wholly into the substrates to catalyse the reactions or else the reaction is inhibited.
Besides the haemoglobin and myoglobin both maps as a O bearer in blood and musculuss severally. Both these proteins contain heme prosthetic group to which the O binds. ” In myoglobin, the haem prosthetic group is not covalently bound to it and is indispensable for its activity. The four polypeptide ironss in hemeglobin, two I± and two I? are bound together tetrahedrally to organize spherical form as shown in the figure below. The I± spirals can adhere four molecules of O “ ( Hames and Nigel, 2004 ) .
Fig. 5 ( Beginning: Diwan, 2008 )
Lipoproteins transport H2O indissoluble lipoids and cholesterin in our organic structure. It has the hydrophilic group confronting outsite. Triglyceride fats and cholesterin ester are carried shielded from H2O by the phospholipid monolayer and the apoprotein as shown in the figure above. ( Diwan, 2008 )
There are two major groups of protein which are differentiated based on their constructions.
aˆ? A protein which is long and thin is the hempen protein.
aˆ? The spherical protein in which the I± spirals and I? constructions are short and interspersed with indiscriminately coiled part and compact construction forms the ball-shaped proteins.
The hempen proteins are typically responsible for the construction of cells, tissues and beings. Some of the hempen proteins are collagen ( protein of sinew, gristle and bone ) , elastin, silk, and ceratins ( proteins of hairs and nails ) .
Fig. 6 ( Beginning: Mcdarby, 2009 )
It is the major protein constituent of sinew, gristle, bone, tegument and blood vass. It provides tensile strength. It consist of three polypeptide ironss. These three polypeptides come together to organize a ternary coiling construction held together by H bonds. In sinews, it forms rope like fibers of high tensile strength and in tegument it forms fibers that can spread out in all waies supplying strength ( Hames and Nigel, 2004 ) .
aˆ? The Keratins
It is the protein of tegument, hairs, wool, graduated tables, plumes and nails which provide strength. The I± keratins contain cysteine residues and hence contains many disulfide bonds.the I± ceratin is a coiling construction. The two strands are wound about each other to organize super twisted spiral. This supertwisting supply the overall strength to the constructions.
In this type of proteins, the polypeptide ironss are tightly folded into compact spherical or ball-shaped forms. They normally maps for cell mobility. This includes transport proteins such as haemoglobin ( transport O in blood ) and myoglobin ( conveyance O in musculuss ) , the contractile proteins such as myosin ( thick fibril of sarcostyle ) and actin ( thin fibril of sarcostyle ) and the storage proteins such as egg white ( egg white protein ) and casein ( milk protein ) . ( Lehninger, 1995 ) .
We have by now found out that the concluding Three Dimensional construction of proteins is the consequence of its amino acid sequence in primary construction, because we found out that the forces responsible for stabilising the 3D construction such as hydrophobic interactions and H bonds are as a consequence from the amino acids sequence in its polypeptide. So the sequence of aminic acids is really of import for finding the 3D construction.
Besides found out that the construction determines the map of assorted proteins. Different amino acid sequence has different construction which in bend has different maps. For illustration the haemoglobin is different from casein. The former is a bearer protein and the later is a storage protein. They have different constructions and hence they functions otherwise.
Therefore we conclude that the amino acerb sequence determines the construction of the proteins and in bend constructions determine the several maps of the proteins.