The linear sequence of amino acids within a protein is considered the primary structure of the protein. Proteins are built from a set of only twenty amino acids, each of which has a unique side chain.

Proteins have four levels of structure: primary (amino acid sequence), secondary (local folding patterns like alpha helices and beta sheets), tertiary (overall 3D shape), and quaternary (assembly of ...

tertiary structure, and often begins co-translationally. Protein folding requires chaperones and often involves stepwise establishment of regular secondary and supersecondary structures ...