In biochemistry, a dimer is a macromolecular complex formed by two, usually non-covalently bound, macromolecules such as proteins or nucleic acids. (The word dimer has roots meaning "two parts", di- + -mer.) It is a quaternary structure of a protein.
A homodimer is formed by two identical molecules (a process called homodimerisation). A heterodimer is formed by two different macromolecules (called heterodimerisation).
Most dimers in biochemistry are not connected by covalent bonds. An example of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different amino acid chains. An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO.
Some proteins contain specialized domains to ensure dimerization (dimerization domains).
- Receptor tyrosine kinases
- Transcription factors
- 14-3-3 proteins
- G protein-coupled receptors
- G protein βγ-subunit dimer
- Triosephosphateisomerase (TIM)
- Alcohol dehydrogenase
- Factor XI
- Factor XIII
- Toll-like receptor
- Variable surface glycoproteins of the Trypanosoma parasite
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