Abstract:
Proteins are one of the four essential components (nucleic acids, proteins, carbohydrates
and lipids) of all living systems. They perform a wide spectrum of functions
ranging from catalysis, signal transduction, maintaining electrochemical potentials in
intra- and extra-cellular regions through the transport of molecules and ions across cell
membranes, and providing rigidity to cells and tissues. Proteins are polymers of amino
acids which are covalently linked to each other to form a polypeptide chain [1]. The
sequence of amino acids across the polymer chain forms the primary structure of a
protein. This sequence, to a good extent, determines the structure of the protein [2]. The
folding of long polypeptide chain give rise to different kinds of local structures, called
the secondary structure of a protein. -helix and -sheet are the two most prominent
structural elements among several secondary structures of proteins. These two structural
elements connect through other secondary structural motifs (small 3/10-helices,
random coils, etc.) to produce an overall proper fold termed as the tertiary structure of
a protein [3]. The association of more than one tertiary structural units may result in a
quaternary structure. A quaternary structure can be an assembly of either homomeric
subunits or heteromeric subunits [1, 3]. A well-known example of a quaternary structure
is haemoglobin consisting of two 2 2-units of myoglobins.
