Domain

In biochemistry, a domain is a combination of elements of the secondary structure (α-helices, β-sheets) of a protein. It represents a complex, folded globular unit. A domain is composed of a clearly defined section of a polypeptide chain. This section usually contains between 50 and 350 amino acid residues. Small proteins often contain only one domain. Larger proteins may contain several domains. These are mostly connected by less structured chain regions.

The shortest domains, such as the zinc finger domain, are stabilized by metal ions or disulfide bridges.

Domains are very often encoded by single exons.

In general, functional domains and structural domains are defined:

• Functional domains are associated, for example, with the activity of an enzyme. Its enzymatic function can be determined by genetically exchanging amino acid residues of the protein domain. If, for example, the catalytic activity of an enzyme changes, this gives an indication of the assignment of the amino acid residue in question.
• Structural domains are areas that have an independent folding (secondary structure). The folding or spatial structure of the peptide segment is partially encoded in the peptide sequence (primary structure) and is supported by chaperones.

A protein domain can be used in completely different proteins. In evolutionary terms, this enables an increased speed in the formation of new proteins, as protein chains can be assembled without problems due to this modular design.

1. Anfinsen CB et al (1961) The kinetics of formation of native ribonuclease during oxidation of the reduced polypeptide chain". Proceedings of the National Academy of Sciences of the United States of America 47: 1309-1312.
2. Bennett MJ et al (1995) 3D domain swapping: a mechanism for oligomer assembly. Protein Science 4: 2455-2468.
3. Cordes MH et al (1996) Sequence space, folding and protein design". Current Opinion in Structural Biology 6: 3-10.
4. Garel J (1992) Folding of large proteins: multidomain and multisubunit proteins. In Creighton T (Ed). Protein Folding(First ed). New York: W.H. Freeman and Company. S 405–454.
5. Ghélis C et al (1979) Conformational coupling between structural units. A decisive step in the functional structure formation. Comptes Rendus de l'Académie des Sciences, Série D. 289: 197-199.
6. Jones S et al. (1998) Domain assignment for protein structures using a consensus approach: characterization and analysis" Protein Science. 7: 233–242.
7. Phillips DC (1966) The three-dimensional structure of an enzyme molecule". Scientific American. 215: 78-84
8. Wheelan SJ et al. (2000) Domain size distributions can predict domain boundaries. Bioinformatics. 16: 613-620