Tertiary Structure

The tertiary structure is the complete three-dimensional structure of a polypeptide chain. Many polypeptides fold into compact, globular structures in which amino acid residues that are distant from each other in primary structure come into close proximity in the folded structure. Because of efficient packing, most water molecules are excluded from the protein's interior. It is the different interactions between the side chains of the amino acids that stabilize the tertiary structure. A major force stabilizing the tertiary structure is the hydrophobic interaction among nonpolar side chains in the core of the protein.

Additional stabilizing forces include electrostatic interactions between ionic groups of opposite charge, hydrogen bonds between polar groups, and disulfide bonds. Disulfide (S–S) bonds are formed between the thiol (S–H) groups of two cysteine side chains resulting in a covalent bond between the two side chains. Many physical and chemical agents, including heat, detergents, salts, heavy metals, strong acids and bases, organic solvents, and mechanical stress, can disrupt or destroy the three-dimensional structure of a protein. This process of destroying the three-dimensional protein structure is called denaturation.

Bibliography

McPherson, Alexander (1989). "Macromolecular Crystals: The Growth of Crystals Is Now the Key to Deducing the Structure of Large Molecules." Scientific American 260(3): 62–69.

Prusiner, Stanley B. (1995). "The Prion Diseases." Scientific American 272(1): 48–57.

Roberts, E. S.; Hopkins, N. E.; and Zaluzec, E. J.; et al. (1994). "Identification of Active-Site Peptides from [³H]2-ethynylnaphthalene-inactivated P450 2B1 and 2B4 Using Amino Acid Sequencing and Mass Spectrometry." Biochemistry 33: 3,766–3,771.