Tertiary and Quaternary Structure
Part II. C. Examples with Complex Structures
Figure 12A. Quaternary Structure of an Antibody. Antibodies, like the IgG form, have 4 polypeptide chains: 2 light chains (L) and 2 heavy chains (H). In the close-up are shown the disulfide bonds within each chain are shown as well as the pair of disulfide bonds between the 2 H chains. Disulfide bonds between polypeptide chains are unusual and found in antibodies and only a few other proteins with the insulin receptor being one of them.
Figure 12B. 3-D structure model of an IgG molecule.
Figure 13. Quaternary Structure of Aspartate Transcarbamoylase (an enzyme from E. Coli). The enzyme has two types of subunits with difference in size: the smaller is the regulatory subunit and the large is the catalytic subunit.
©Wilbur H. Campbell, 1995; wcampbel@mtu.edu