The quaternary protein structure refers to the orientation and arrangement of subunits in proteins with multi-subunits. This is only relevant for proteins with multiple polypeptide chains.

The structure of a protein is hierarchically arranged, from a primary to quaternary structure. The wide variation in amino acid sequences accounts for the different conformations in protein structure.

structural biology makes use of some fundamental concepts related to the hierarchical assembly of proteins and nucleic acids (such as macromolecule structure; primary, secondary, tertiary and ...

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 ...