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Structure of a Protein
The Peptide bonds are formed by the condensation of amino acids to form protein structures. The fundamental structure of protein is the sequence of amino acids that make up the protein. The dihedral angles of peptide bonds determine the secondary structure, while the folding of protein chains in space determines the tertiary structure. The quaternary structure is formed with the help of folded polypeptide units with complex functional proteins.
Protein Structure is divided into four categories: primary, secondary, tertiary, and quaternary.
Proteins’ Classification
Proteins are divided into two categories based on their molecular form.
- Fibrous Proteins: A fiber-like structure is formed when polypeptide chains run parallel and are held together by hydrogen and disulfide bonds. These proteins are water insoluble. These are proteins that aren’t soluble in water. Keratin (found in hair, wool, and silk) and myosin (found in muscles), for example.
- Globular Proteins: This structure is formed when polypeptide chains coil around each other to form a spherical shape. These are frequently water soluble. Insulin and albumin are examples of globular proteins.
Protein Structure Levels
Proteins Basic Structure
The primary structure is the specific ordering of amino acids that make up their chains.The perfect sequence of proteins is critical since it defines the protein’s ultimate fold and, as a result, its function.
The Proteins are made up of a large number of polypeptide chains linked together. Organization of amino acids in these chains has a specific sequence that is unique to each protein. Any alteration in the protein’s sequence has an impact on the complete protein.
The amino acid sequence within the polypeptide chain is critical for the proper functioning of the protein, as you we can imagine. The genetic code of DNA encrypts this sequence if there is a mutation in the DNA protein function can be harmed and the amino acid sequence is altered.
The amino acid sequence in the polypeptide chain is the protein’s fundamental structure. The core structure of a protein is maintained by covalent peptide bonds that connect the amino acids.All known genetic illnesses, including as cystic fibrosis, sickle cell anemia, albinism, and others, are produced by mutations that create changes in primary protein structures, which then cause changes in secondary, tertiary, and presumably quarterly structures.
Amino acids are very small chemical compounds having four substituents and a chiral carbon. Only the fourth amino acid’s side chain differs from the others.
Protein Secondary Structure
Local folded structures that arise within a polypeptide due to interactions between atoms of the backbone are referred to as secondary structure of protein.
These Proteins are made up of more than just polypeptide chains.The interaction between the amine and carboxyl groups of the peptide link causes these polypeptide chains to fold.
The structure gives a possible shape of a lengthy polypeptide chain.
It can be found in two main kinds of structures:
helix and pleated sheet forms.
These structures are not formed by hydrogen bonding between the -CO and -NH groups of the peptide bond, which causes the backbone of the polypeptide chain to fold in a regular pattern.
Segments of the protein chain, on the other hand, may develop their own local fold, which is more simple and commonly takes the form of a spiral, expanded curve, or loop. These elements are local folds that make up a protein’s secondary structure.
(a) – Helix: – Helix is one of the most popular ways for a polypeptide chain to create all potential hydrogen bonds by twisting into a right-handed screw and hydrogen-bonding the -NH group of each amino acid residue to the -CO of the next turn of the helix. The polypeptide chains are twisted to form a right handed screw .
(b) – pleated sheet: The polypeptide chains are stretched out next one another and then connected by intermolecular H-bonds in this arrangement. The peptide chains are stretched to nearly maximum extension and then arranged side by side in this structure which is kept together by intermolecular hydrogen bonds.
Protein Tertiary Structure
By additional folding of the protein’s secondary structure,the tertiary structure is obtained.
This structure is stabilised by H-bonds, electrostatic forces, disulphide connections, and Vander Waals forces.
The total folding of the polypeptide chains is represented by the tertiary structure of proteins, which is additional folding of the secondary structure.
Fibrous and globular molecule morphologies are two of the most common.
Hydrogen bonds, disulphide connections, van der Waals, and electrostatic forces of attraction are the major forces that stabilise the secondary and tertiary structures of proteins.
Protein Quaternary Structure
These structures are formed by the spatial arrangement of numerous tertiary structures. Some proteins are made up of subunits, which are made up of two or more polypeptide chains. It refers to the spatial arrangement of these components in relation to one another.
Each protein folds into its own unique and biologically active three-dimensional fold, known as the tertiary structure, based on its amino acid sequence. Proteins are made up of several secondary components, some of which are simple and others which are more complex. Domains are segments of the protein chain that have their own three-dimensional fold and can be linked to a specific function. Today, these are regarded as the functional and evolutionary building blocks of proteins.
Organic or elemental components are required for the activity and stability of many proteins, the majority of which are enzymes. As a result, studying protein evolution not only provides structural information, but also connects proteins from various regions of the metabolism.
Conclusion
As we can conclude that the base level of the protein hierarchy is the main structure, which is the specific linear sequence of amino acids that makes up one polypeptide chain. Secondary structure is the consistent folding of regions into precise structural patterns within one polypeptide chain, and it is the next level up from primary structure. Secondary structures generally hold hydrogen bonds between the carbonyl oxygen and the peptide link amide hydrogen together. The next level up from secondary structure is tertiary structure, which is the specific three-dimensional arrangement of all the amino acids in a single polypeptide chain. This structure is usually conformational, native, and active, with many noncovalent connections holding it together.
The unique spatial arrangement and interactions of quaternary structure are the next ‘step up’ from tertiary structure between two or more polypeptide chains.
