Definitions of Protein Structure Primary structure-amino acid sequence Secondary structure-local conformation of peptide backbone Tertiary structure-interaction of different secondary structures on same polypeptide Quaternary structure-interaction of different polypeptides in structure that has more than one protein component Definitions of Protein Structure Primary structure – amino acid sequence Secondary structure–local conformation of peptide backbone Tertiary structure– interaction of different secondary structures on same polypeptide Quaternary structure– interaction of different polypeptides in structure that has more than one protein component