In biochemistry, a quaternary structure describes the defined arrangement of two or more macromolecules with a respective tertiary structure , which are held together by hydrogen bonds , van der Waals forces and Coulomb forces .
Structural levels subordinate to the quaternary structure are the primary structure , the secondary structure and the tertiary structure . This classification of the structure hierarchy was proposed in 1952 by Kaj Ulrik Linderstrøm-Lang .
A classic example of quaternary structures are proteins , many of which can be assembled into functional complexes and reversibly separated. The association of the subunits takes place via hydrophobic interactions.
Proteins with a quaternary structure can be differentiated into:
- Fiber proteins (e.g. collagen , elastin , keratin )
- globular proteins (e.g. hemoglobin, myoglobin , ribosome)
- Protein complexes