Question

Briefly explain the four levels of protein structure. In your answer refer to a
protein haemoglobin and catabolite gene activator protein where applicable.

Answer 1

Protein primary structure is the sequence of amino acid residues linked by peptide bonds in the polypeptide chain.

Protein secondary structure is the local ordering of a polypeptide chain fragment stabilized by hydrogen bonds. The most common types of secondary protein structure are α-helices and β-sheets.

Protein tertiary structure is the spatial structure of the polypeptide chain. Structurally, it consists of elements of a secondary structure stabilized by various types of interactions: hydrophobic, ionic, hydrogen, and covalent disulfide bonds.

Protein quaternary structure is the arrangement of several polypeptide chains as part of a single protein complex. As a result, such proteins consist of several subunits synthesized separately. Hemoglobin and catabolite gene activator protein are examples of proteins with quaternary structure.