Medicine & USMLE

Primary Protein Structure

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


The primary structure of proteins refers to the sequence or chain of amino acids. These amino acids are linked together by peptide bonds.

Key Points

  • Primary Structure
    • sequence of amino acids linked together by covalent peptide (amide) bonds
      • Affects protein orientation via rotation of N-C and C-C bonds 
    • Factors affecting primary structure:
      • Protease cleavage of peptide bonds
      • DNA mutagenesis (different amino acids encoded)
    • Note: Protein denaturation (unfolding, loss of 3D shape) does not alter primary structure
      • primary sequence of amino acids is unchanged