Protein dimer

{{Short description|Macromolecular complex formed by two, usually non-covalently bound, macromolecules}}

File:Galactose-1-phosphate uridylyltransferase 1GUP.png 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.{{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 }} An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO.{{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 }}

Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity.{{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}}

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.{{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 |pages=1823 |doi=10.3390/pharmaceutics13111823 |doi-access=free |issn=1999-4923 |pmc=8625816 |pmid=34834237}}