AIM: To classify proteins using the CATH and SCOP databases.

THEORETICAL BACKGROUND:

Proteins (also known as polypeptides) are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.

Most proteins fold into unique 3-dimensional structures. The shape into which a protein naturally folds is known as its native conformation. To describe the complicated macromolecular structure of proteins, biochemists have, for convenience, recognized four basic structural levels of organization of proteins based on the degree of complexity of their molecule. These structural levels were first described by Linderstrom-Lang and are often referred to as primary, secondary, tertiary and quaternary. The first three structural levels can exist in molecules composed of a single polypeptide chain whereas the last one involves interaction of polypeptides within a muiti-chained protein molecule.