Medicine & USMLE

Quaternary Protein Structure

Protein Structure
  1. Primary Protein Structure
  2. Secondary Protein Structure
  3. Tertiary Structure
  4. Quaternary Protein Structure


The quaternary structure of proteins is the highest level of protein structure, and refers to the interactions between separate proteins to form a multiprotein complex. 

Key Points

  • Quaternary Structure
    • Interactions between separate proteins to form a multiprotein complex
    • Involves the same forces as tertiary structures
      • Interactions with water, hydrogen bonding, electrostatic interactions, van der Waals forces, and disulfide bonds


One common example of quaternary structure is the bringing together of 4 globin proteins in hemoglobin. These 4 globin molecules and heme come together to form a single multi-protein complex called hemoglobin, which plays a key role in carrying oxygen in our blood.