Tertiary and Quaternary Structure
Part I. B. Ionic Bonds
B. Ionic Bonds in Tertiary Structure
Ionic bonds form between polar, charged AA side chains:
Negative -- Glu Asp
Positive -- Lys Arg His
Figure 4. Ionic Bonds between AA Side Chains.
Ionic bonds are sometimes called Salt Bridges. Ionic bonds are pH-dependent since the charge is not fixed. However, pKs for AA in the interior of a protein may be very different from the usual pK values for amino acid side chains free in solution. This is called a micro-environment effect and is usually due to the absence of water from the interior of the protein and the presence of other amino acid side chains which can influence the local environment of the side chain of an amino acid.
©Wilbur H. Campbell, 1995; wcampbel@mtu.edu