Tertiary structure

In biochemistry, tertiary structure refers to the specific three-dimensional folding of linear macromolecules (proteins or nucleic acids) into higher-level, spatial structures, whereby primary structures and secondary structures are retained (conformation).

In contrast to the secondary structure, which defines the structure of individual areas of the amino acid or nucleobase sequence, the tertiary structure refers to the complete three-dimensional structure of the chain. In a globular protein, the energetic driving force for the folding of the individual secondary structure elements is described by the Kautzman rule: the hydrophobic areas are on the inside, while the hydrophilic and/or charged areas face the aqueous environment (see also hydrophobic effect). Disulphide bridges are often involved in the stabilization of tertiary structures.

The three-dimensional structure is particularly characteristic of proteins and is essential for their biological function. During or after the production of the protein by translation of an mRNA, the protein is converted into its biologically active form by protein folding. This process is supported by chaperones, among other things.

The most important method for analyzing tertiary structures is X-ray structure analysis.

Tertiary structures can also change, e.g. when conformational changes occur upon binding by substrates or ligands (receptors) or when transcription factors bind to their target DNA sequences.