Protein dimer

In biochemistry, a protein dimer is a macromolecular complex or multimer formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word dimer has roots meaning "two parts", di- + -mer. A protein dimer is a type of protein quaternary structure.

Cartoon diagram of a dimer of Escherichia coli galactose-1-phosphate uridylyltransferase (GALT) in complex with UDP-galactose (stick models). Potassium, zinc, and iron ions are visible as purple, gray, and bronze-colored spheres respectively.

A protein homodimer is formed by two identical proteins while a protein heterodimer is formed by two different proteins.

Most protein 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.^[1] An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO.^[2]

Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity.^[3]

The G protein-coupled cannabinoid receptors have the ability to form both homo- and heterodimers with several types of receptors such as mu-opioid, dopamine and adenosine A2 receptors.^[4]

Examples

• Transcription factors
  • Leucine zipper motif proteins
• 14-3-3 proteins
• Variable surface glycoproteins of the Trypanosoma parasite
• Tubulin
• Some clotting factors
  • Factor XI
  • Factor XIII
  • Fibrinogen
• Some receptors
  • Nuclear receptors
  • G protein βγ-subunit dimer
  • Toll-like receptor
  • Receptor tyrosine kinases
• Some enzymes
  • Type II restriction enzymes
  • Triosephosphateisomerase (TIM)
  • Alcohol dehydrogenase

Alkaline phosphatase

E. coli alkaline phosphatase, a dimer enzyme, exhibits intragenic complementation.^[5] That is, when particular mutant 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 the E. coli alkaline phosphatase allows cooperative interactions between the constituent mutant monomers that can generate a more functional form of the holoenzyme. The dimer has two active sites, each containing two zinc ions and a magnesium ion.[8]

See also

• Dimerization
• Protein trimer
• Oligomer
• ProtCID

References

1. Sluis-Cremer N, Hamamouch N, San Félix A, Velazquez S, Balzarini J, Camarasa MJ (August 2006). "Structure-activity relationships of [2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]- 3'-spiro-5' '-(4' '-amino-1' ',2' '-oxathiole-2' ',2' '-dioxide)thymine derivatives as inhibitors of HIV-1 reverse transcriptase dimerization". J. Med. Chem. 49 (16): 4834–41. doi:10.1021/jm0604575. PMID 16884295.
2. Herscovitch M, Comb W, Ennis T, Coleman K, Yong S, Armstead B, Kalaitzidis D, Chandani S, Gilmore TD (February 2008). "Intermolecular disulfide bond formation in the NEMO dimer requires Cys54 and Cys347". Biochemical and Biophysical Research Communications. 367 (1): 103–8. doi:10.1016/j.bbrc.2007.12.123. PMC 2277332. PMID 18164680.
3. Amoutzias, Grigoris D.; Robertson, David L.; Van de Peer, Yves; Oliver, Stephen G. (2008-05-01). "Choose your partners: dimerization in eukaryotic transcription factors". Trends in Biochemical Sciences. 33 (5): 220–229. doi:10.1016/j.tibs.2008.02.002. ISSN 0968-0004. PMID 18406148.
4. Filipiuc, Leontina Elena; Ababei, Daniela Carmen; Alexa-Stratulat, Teodora; Pricope, Cosmin Vasilica; Bild, Veronica; Stefanescu, Raluca; Stanciu, Gabriela Dumitrita; Tamba, Bogdan-Ionel (2021-11-01). "Major Phytocannabinoids and Their Related Compounds: Should We Only Search for Drugs That Act on Cannabinoid Receptors?". Pharmaceutics. 13 (11): 1823. doi:10.3390/pharmaceutics13111823. ISSN 1999-4923. PMC 8625816. PMID 34834237.
5. Hehir, Michael J.; Murphy, Jennifer E.; Kantrowitz, Evan R. (2000). "Characterization of Heterodimeric Alkaline Phosphatases from Escherichia coli: An Investigation of Intragenic Complementation". Journal of Molecular Biology. 304 (4): 645–656. doi:10.1006/jmbi.2000.4230. PMID 11099386.

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.