{{Short description|Macromolecular complex formed by two, usually non-covalently bound, macromolecules}} [[File:Galactose-1-phosphate uridylyltransferase 1GUP.png|thumb|right|Ribbon diagram of a dimer of ''Escherichia coli'' galactose-1-phosphate uridylyltransferase (GALT) in complex with UDP-galactose. Potassium, zinc, and iron ions are visible as purple, gray, and bronze-colored spheres respectively.]]
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.
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.<ref name="pmid16884295">{{cite journal |vauthors=Sluis-Cremer N, Hamamouch N, San Félix A, Velazquez S, Balzarini J, Camarasa MJ | title = 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 | journal = J. Med. Chem. | volume = 49 | issue = 16 | pages = 4834–41 |date=August 2006 | pmid = 16884295 | doi = 10.1021/jm0604575 }}</ref> An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO.<ref name="pmid18164680">{{cite journal |vauthors=Herscovitch M, Comb W, Ennis T, Coleman K, Yong S, Armstead B, Kalaitzidis D, Chandani S, Gilmore TD | title = Intermolecular disulfide bond formation in the NEMO dimer requires Cys54 and Cys347 | journal = Biochemical and Biophysical Research Communications | volume = 367 | issue = 1 | pages = 103–8 |date=February 2008 | pmid = 18164680 | pmc = 2277332 | doi = 10.1016/j.bbrc.2007.12.123 }}</ref>
Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity.<ref>{{Cite journal|last1=Amoutzias|first1=Grigoris D.|last2=Robertson|first2=David L.|last3=Van de Peer|first3=Yves|last4=Oliver|first4=Stephen G.|date=2008-05-01|title=Choose your partners: dimerization in eukaryotic transcription factors|journal=Trends in Biochemical Sciences|volume=33|issue=5|pages=220–229|doi=10.1016/j.tibs.2008.02.002|issn=0968-0004|pmid=18406148}}</ref>
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.<ref>{{Cite journal |last1=Filipiuc |first1=Leontina Elena |last2=Ababei |first2=Daniela Carmen |last3=Alexa-Stratulat |first3=Teodora |last4=Pricope |first4=Cosmin Vasilica |last5=Bild |first5=Veronica |last6=Stefanescu |first6=Raluca |last7=Stanciu |first7=Gabriela Dumitrita |last8=Tamba |first8=Bogdan-Ionel |date=2021-11-01 |title=Major Phytocannabinoids and Their Related Compounds: Should We Only Search for Drugs That Act on Cannabinoid Receptors? |journal=Pharmaceutics |volume=13 |issue=11 |page=1823 |doi=10.3390/pharmaceutics13111823 |doi-access=free |issn=1999-4923 |pmc=8625816 |pmid=34834237}}</ref>
== 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 *Some viral proteins **Mammarenaviruses Z matrix protein <ref>{{Cite journal |last1=Witwit |first1=Haydar |last2=de la Torre |first2=Juan C. |date=2025-04-29 |title=Mammarenavirus Z Protein Myristoylation and Oligomerization Are Not Required for Its Dose-Dependent Inhibitory Effect on vRNP Activity |journal=BioChem |language=en |volume=5 |issue=2 |page=10 |doi=10.3390/biochem5020010 |doi-access=free |issn=2673-6411|pmc=12163724 }}</ref><ref>{{Cite journal |last=Witwit |first=Haydar |last2=Ibanez |first2=Pablo |last3=Zhou |first3=Ruifeng |last4=Jackson |first4=Nathaniel |last5=Escobedo |first5=Ruby |last6=Cubitt |first6=Beatrice |last7=Khafaji |first7=Roaa |last8=Sattler |first8=Rachel Y. |last9=Martinez-Sobrido |first9=Luis |last10=de la Torre |first10=Juan Carlos |date=2026-02-04 |title=Prolyl tRNA Synthetase Is Required for Mammarenavirus Multiplication |url=https://www.mdpi.com/1999-4915/18/2/202 |journal=Viruses |language=en |volume=18 |issue=2 |page=202 |doi=10.3390/v18020202 |doi-access=free|issn=1999-4915}}</ref><ref>{{Cite journal |last=Witwit |first=Haydar |last2=Betancourt |first2=Carlos Alberto |last3=Cubitt |first3=Beatrice |last4=Khafaji |first4=Roaa |last5=Kowalski |first5=Heinrich |last6=Jackson |first6=Nathaniel |last7=Ye |first7=Chengjin |last8=Martinez-Sobrido |first8=Luis |last9=de la Torre |first9=Juan C. |date=2024-08-26 |title=Cellular N-Myristoyl Transferases Are Required for Mammarenavirus Multiplication |url=https://www.mdpi.com/1999-4915/16/9/1362 |journal=Viruses |language=en |volume=16 |issue=9 |page=1362 |doi=10.3390/v16091362 |doi-access=free|issn=1999-4915 |pmc=11436053 |pmid=39339839}}</ref><ref>{{Cite journal |last=Witwit |first=Haydar |last2=de la Torre |first2=Juan C. |date=2025-10-01 |title=N-myristoyltransferase inhibitors as candidate broad-spectrum antivirals to treat viral infections promoted by immunosuppression associated with JAK inhibitors therapy |url=https://www.sciencedirect.com/science/article/pii/S0166354225001846 |journal=Antiviral Research |volume=242 |article-number=106258 |doi=10.1016/j.antiviral.2025.106258 |issn=0166-3542|url-access=subscription }}</ref>
==Alkaline phosphatase==
''E. coli'' alkaline phosphatase, a dimer enzyme, exhibits intragenic complementation.<ref>{{Cite journal |doi=10.1006/jmbi.2000.4230|title=Characterization of Heterodimeric Alkaline Phosphatases from Escherichia coli: An Investigation of Intragenic Complementation |year=2000 |last1=Hehir |first1=Michael J. |last2=Murphy |first2=Jennifer E. |last3=Kantrowitz |first3=Evan R. |journal=Journal of Molecular Biology |volume=304 |issue=4 |pages=645–656 |pmid=11099386 }}</ref> 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.<ref>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.</ref>
==See also== * Dimerization * Protein trimer * Oligomer * ProtCID
==References== {{reflist}} * Conn. (2013). ''G protein coupled receptors modeling, activation, interactions and virtual screening'' (1st ed.). Academic Press. * Matthews, Jacqueline M. ''Protein Dimerization and Oligomerization in Biology''. Springer New York, 2012.
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{{DEFAULTSORT:Protein dimer}} Category:Protein structure Category:Dimers (chemistry) Category:Protein complexes