Tertiary and Quaternary Structure
Part II. B. Examples of Quaternary Structure
B. Examples of Quaternary Structure in Proteins
Figure 9A. Hemoglobin Tetramer showing positions of the 4 polypeptide chains.
Figure 9B. Hemoglobin Tetramer with more detail shown of 4 polypeptide chains and interfaces between them. The subunits of hemoglobin are held together by non-covalent ionic bonds.
This figure taken from Voet - Biochemistry - © 1990, John Wiley & Sons.
Figure 10. Dimer showing interface of the 2 polypeptide chains.
Figure 11. Glutathione Reductase Dimer which has distinct domains or subparts of each subunit for binding substrates and cofactors to the enzyme. Blue domain is for substrate NADP+; Pink domain is for binding cofactor FAD; and Cream domain is at the interface between the two subunits. The Green box shows the active site of the enzyme where the other substrate Glutathione binds.
Figure taken from Stryer, Biochemistry, 2nd Ed., © 1975, 1991 Lubert Stryer.
©Wilbur H. Campbell, 1995; wcampbel@mtu.edu