Quaternary structure

Definition

Quaternary structure is the highest level of protein structure, involving the assembly of multiple polypeptide chains into a functional protein complex. These interactions are stabilized by non-covalent bonds and sometimes disulfide bonds.

5 Must Know Facts For Your Next Test

1. Quaternary structures are formed by the interaction of two or more polypeptide subunits.
2. Hemoglobin is a classic example of a protein with quaternary structure, consisting of four subunits.
3. The stability and function of quaternary structures depend on non-covalent interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions.
4. Changes in environmental conditions like pH, temperature, or ionic strength can affect quaternary structure.
5. Quaternary structures allow proteins to have regulatory mechanisms and cooperative binding properties.

Review Questions

• What types of interactions stabilize quaternary structures?
• Give an example of a protein that has a quaternary structure.
• How does the quaternary structure contribute to the functionality of a protein?

Related terms

Primary Structure:

The linear sequence of amino acids in a polypeptide chain.

Secondary Structure:

Local folding patterns within a polypeptide chain, such as alpha-helices and beta-sheets.

Tertiary Structure:

The three-dimensional shape formed by an entire polypeptide chain, including folds and bends.