Inbiochemistry, aprotein dimer is a macromolecular complex ormultimer formed by two protein monomers, or single proteins, which are usuallynon-covalently bound. Manymacromolecules, such asproteins ornucleic acids, form dimers. The worddimer has roots meaning "two parts",di- +-mer. A protein dimer is a type ofprotein quaternary structure.
A proteinhomodimer is formed by two identicalproteins while a proteinheterodimer is formed by two different proteins.
Most protein dimers in biochemistry are not connected bycovalent bonds. An example of a non-covalent heterodimer is the enzymereverse transcriptase, which is composed of two differentamino acid chains.[1] An exception is dimers that are linked bydisulfide bridges such as the homodimeric proteinNEMO.[2]
Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity.[3]
TheG protein-coupledcannabinoid receptors have the ability to form both homo- and heterodimers with several types of receptors such asmu-opioid,dopamine andadenosine A2 receptors.[4]
E. colialkaline phosphatase, a dimer enzyme, exhibitsintragenic complementation.[5] That is, when particularmutant versions of alkaline phosphatase were combined, the heterodimeric enzymes formed as a result exhibited a higher level of activity than would be expected based on the relative activities of the parental enzymes. These findings indicated that the dimer structure of theE. coli alkaline phosphatase allows cooperative interactions between the constituent mutant monomers that can generate a more functional form of theholoenzyme. The dimer has two active sites, each containing two zinc ions and a magnesium ion.[8]
6. Conn. (2013).G protein coupled receptors modeling, activation, interactions and virtual screening (1st ed.). Academic Press.
7. Matthews, Jacqueline M.Protein Dimerization and Oligomerization in Biology. Springer New York, 2012.
8. Hjorleifsson, Jens Gu[eth]Mundur, and Bjarni Asgeirsson. “Cold-Active Alkaline Phosphatase Is Irreversibly Transformed into an Inactive Dimer by Low Urea Concentrations.”Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, vol. 1864, no. 7, 2016, pp. 755–765, https://doi.org/10.1016/j.bbapap.2016.03.016.
