Fibrous proteins contain secondary structures such as α-helices or β-pleated sheets. As a result of the rod-like or sheet-like shapes, fibrous proteins have structural than dynamic roles.
Protein contains four subunits designated to α and β. Each subunit contains a haem group that binds reversibly with O2. The nine highly conserved amino acid residues in haemoglobin are given in Table 3.1. Table 3.1 Highly Conserved Amino Acid Residues in Haemoglobin Position Amino acid Role F8 Histidine Proximal haem-linked histidine E7 Histidine Distal haem-linked…
A fourth degree of complexity in protein structure has been recognised, which is known as quaternary structure. High molecular weight proteins are composed of several polypeptide chains. Each polypeptide components is called subunit. Subunits in a protein complex may be identical or quite different. The identical peptides in a polypeptide are referred to as oligomers.…
Covalent bond is formed between two cysteine amino acid residues; as a result, disulphide bonds are formed. An example is cystine.
When a group containing a hydrogen atom is covalently bonded to an electronegative atom, such as O2 or nitrogen favours hydrogen bonding. A hydrogen bond is formed when an H2 atom shares electrons with two neighbouring atoms, that is, oxygen and nitrogen. Example: Hydrogen atom of one peptide shares its electron with the carbonyl atom of another peptide.…
Electrostatic bonds are formed when two oppositely charged groups come close together and attract each other. Example: Divalent cations like Mg2+ may form electrostatic bonds with two acidic side chains. Interaction between acidic and basic groups of amino acid: The R—group of glutamic and aspartic acid contributes negatively charged carboxylate groups, and the basic amino acids (arginine,…
As polypeptide folds, hydrophobic R—groups are brought into close proximity as they are excluded from water. Many amino acids like valine, alanine, leucine, isoleucine, methionine, tryptophan, phenylalanine, and tyrosine have side chain or R groups which are hydrophilic. These R—groups combine together with the removal of hydrogen and form linkages between various segments of chains.…