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.

Figure 1. This structure of myoglobin illustrates a typical tertiary structure.
Figure 1. This structure of myoglobin illustrates a typical tertiary structure.

SEE ALSO Primary Structure ; Quaternary Structure ; Secondary Structure .

Elizabeth S. Roberts-Kirchhoff


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