In biochemistry, the tertiary structure of a protein is its overall shape. All protein molecules are simple unbranched chains of amino acids, but it is by coiling into a specific three-dimensional shape that they are able to perform their biological function. The tertiary structure that a protein assumes to carry out its physiological role inside a cell is known as the native state or sometimes the native conformation. A protein assumes tertiary structure by "folding". An important type of chemical bond involved in stabilizing the tertiary structure of many proteins is the disulfide bond.
One goal of bioinformatics is to predict the native conformation of a protein from its primary sequence. Conventionally, tertiary structures are deduced through crystallography or multidimensional NMR. The study of protein tertiary structure is known as structural biology.