Guest lecture given on structural organization of proteins

STRUCTURAL ORGANIZATION OF PROTEINS

Date- 27^TH April, 2025                                                                      

Faculty : Dr P. Mary Anupama, Head, Dept of Biochemistry,  Dept. of Biochemistry.

Total students present- 15

 Target group: PG chemistry students

Proteins, the essential building blocks of life, are organized into four levels of structural complexity: primary, secondary, tertiary, and quaternary. The primary structure is the linear sequence of amino acids, while the secondary structure involves local folding into α-helices and β-sheets. The tertiary structure is the overall three-dimensional shape of a single polypeptide chain, and the quaternary structure describes the arrangement of multiple polypeptide chains (subunits) in multi-subunit proteins. 

Primary Structure:

This level defines the exact sequence of amino acids in a protein, which is determined by the genes coding for that specific protein. Each amino acid is connected to the next by a peptide bond, forming a linear chain. 

 Secondary Structure:

This level involves local folding of the polypeptide chain due to hydrogen bonding between the amino and carbonyl groups of the peptide backbone. Common secondary structures include α-helices (coiled structures) and β-pleated sheets (sheet-like structures). 

 Tertiary Structure:

This level describes the overall three-dimensional shape of a single polypeptide chain, including all of the secondary structural elements. This shape is determined by interactions between the side chains (R-groups) of the amino acids, which can include hydrophobic interactions, hydrogen bonds, salt bridges, and disulfide bonds. 

 Quaternary Structure:

This level is only present in proteins that consist of multiple polypeptide chains (subunits). The subunits interact with each other through the same types of interactions that determine tertiary structure, forming a complex three-dimensional structure