Tertiary and Quaternary Structure
Part I. A. Tertiary Structure
Part I. Tertiary Structure - The 3rd Level of Protein Structure
Tertiary structure is formed by long distance interactions of the Amino Acid side chains.
There are several types of bonds:
Hydrogen bonds
Ionic bonds
Hydrophobic interactions
Disulfide bonds -- weak covalent bond between 2 Cys (R-Cys-S-S-Cys-R)
Figure 2. Summary of the Bonding Stabilizing Protein Structure. A. Ionic bond; B. Hydrogen bond (3 types shown); C. Hydrophobic interaction (2 forms shown - lower is cluster type, while upper is Pi-bond type; D. Disulfide bond. This figure is borrowed from an old Conn & Stumpf Outlines of Biochemistry Text who owns the copyright.
A. Hydrogen Bonds in Tertiary Structure
Hydrogen bonds in tertiary structure involve polar Non-charged Amino Acid side chains:
Alcohols -- Ser Thr Tyr
Amides --- Asn Gln
Figure 3. Hydrogen Bonds between AA Side Chains.
These AAs can serve as both H-donors and acceptors. These are weak bonds like all H-bonds.
In some cases, the acids (Glu and Asp) and His - when not charged - form Hydrogen Bonds.
Cys thiols (-S-H) do not form Hydrogen bonds (very often).
©Wilbur H. Campbell, 1995; wcampbel@mtu.edu