The term
protein tertiary structure refers to a
protein's geometric shape. The tertiary structure will have a single
polypeptide chain "backbone" with one or more
protein secondary structures, the
protein domains.
Amino acid side chains may interact and bond in a number of ways. The interactions and bonds of side chains within a particular protein determine its tertiary structure. The protein tertiary structure is defined by its
atomic coordinates. These coordinates may refer either to a protein domain or to the entire tertiary structure. A number of tertiary structures may fold into a
quaternary structure.