Protein subunit: Difference between revisions
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{{Short description| | {{Short description|Structural unit of a protein complex}} | ||
[[Image:HLA-A11.png|thumb|274px|right|Rendering of [[HLA-A11]] showing the <span style="color:#00CBC8;">α (A*1101 gene product)</span> and <span style="color:#F08080;">β (Beta-2 microglobulin)</span> subunits. This receptor has a <span style="color:#EEC700;">bound peptide</span> (in the [[binding pocket]]) of heterologous origin that also contributes to function.]] | [[Image:HLA-A11.png|thumb|274px|right|Rendering of [[HLA-A11]] showing the <span style="color:#00CBC8;">α (A*1101 gene product)</span> and <span style="color:#F08080;">β (Beta-2 microglobulin)</span> subunits. This receptor has a <span style="color:#EEC700;">bound peptide</span> (in the [[binding pocket]]) of heterologous origin that also contributes to function.]] | ||
In [[structural biology]], a '''protein subunit''' is a [[polypeptide chain]] or single [[protein]] molecule that assembles (or "''coassembles''") with others to form a [[protein complex]].<ref name="Stoker">{{cite book |last1=Stoker |first1=H. Stephen |title=General, Organic, and Biological Chemistry |date=1 January 2015 |publisher=Cengage Learning |location=Boston, MA |isbn=978-1-305-68618-2 |pages=709–710 |edition=7th |url=https://books.google.com/books?id=IBGdBQAAQBAJ&pg=PA709 |access-date=15 April 2022 |language=en}}</ref><ref name="Smith">{{cite book |last1=Smith |first1=Michael B. |title=Biochemistry: An Organic Chemistry Approach |date=27 April 2020 |publisher=CRC Press |location=Boca Raton |isbn=978-1-351-25807-4 |pages=269–270 |url=https://books.google.com/books?id=0TXfDwAAQBAJ&pg=PA269 |access-date=15 April 2022 |language=en}}</ref><ref name="Alberts">{{cite book |last1=Alberts |first1=Bruce |last2=Johnson |first2=Alexander |last3=Lewis |first3=Julian |last4=Raff |first4=Martin |last5=Roberts |first5=Keith |last6=Walter |first6=Peter |title=The Shape and Structure of Proteins |date=2002 |publisher=Garland Science |location=New York |url=https://www.ncbi.nlm.nih.gov/books/NBK26830/ |access-date=15 April 2022 |language=en}}</ref> | In [[structural biology]], a '''protein subunit''' is a [[polypeptide chain]] or single [[protein]] molecule that assembles (or "''coassembles''") with others to form a [[protein complex]].<ref name="Stoker">{{cite book |last1=Stoker |first1=H. Stephen |title=General, Organic, and Biological Chemistry |date=1 January 2015 |publisher=Cengage Learning |location=Boston, MA |isbn=978-1-305-68618-2 |pages=709–710 |edition=7th |url=https://books.google.com/books?id=IBGdBQAAQBAJ&pg=PA709 |access-date=15 April 2022 |language=en}}</ref><ref name="Smith">{{cite book |last1=Smith |first1=Michael B. |title=Biochemistry: An Organic Chemistry Approach |date=27 April 2020 |publisher=CRC Press |location=Boca Raton |isbn=978-1-351-25807-4 |pages=269–270 |url=https://books.google.com/books?id=0TXfDwAAQBAJ&pg=PA269 |access-date=15 April 2022 |language=en}}</ref><ref name="Alberts">{{cite book |last1=Alberts |first1=Bruce |last2=Johnson |first2=Alexander |last3=Lewis |first3=Julian |last4=Raff |first4=Martin |last5=Roberts |first5=Keith |last6=Walter |first6=Peter |title=The Shape and Structure of Proteins |date=2002 |publisher=Garland Science |location=New York |url=https://www.ncbi.nlm.nih.gov/books/NBK26830/ |access-date=15 April 2022 |language=en}}</ref> | ||
Large assemblies of proteins such as [[viruses]] often use a small number of types of protein subunits as building blocks.<ref name="Kumar">{{cite book |editor-last1=Vijayan |editor-first1=M. |editor-last2=Yathindra |editor-first2=N. |editor-last3=Kolaskar |editor-first3=A. S. |author-last1=Kumar |author-first1=A. |author-last2=Evarsson |author-first2=A. |author-last3=Hol |author-first3=W. G. J. |title=Perspectives in Structural Biology: A Volume in Honour of G.N. Ramachandran | chapter=Multi-protein assemblies with point group symmetry |date=1999 |publisher=Universities Press |location=Hyderabad, India |isbn=978-81-7371-254-8 |pages=449–466 |chapter-url=https://books.google.com/books?id=xTy_M3B5sf4C&pg=PA462 |access-date=15 April 2022 |language=en}}</ref><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 |pages=10 |doi=10.3390/biochem5020010 |doi-access=free |issn=2673-6411}}</ref> | Large assemblies of proteins such as [[viruses]] often use a small number of types of protein subunits as building blocks.<ref name="Kumar">{{cite book |editor-last1=Vijayan |editor-first1=M. |editor-last2=Yathindra |editor-first2=N. |editor-last3=Kolaskar |editor-first3=A. S. |author-last1=Kumar |author-first1=A. |author-last2=Evarsson |author-first2=A. |author-last3=Hol |author-first3=W. G. J. |title=Perspectives in Structural Biology: A Volume in Honour of G.N. Ramachandran | chapter=Multi-protein assemblies with point group symmetry |date=1999 |publisher=Universities Press |location=Hyderabad, India |isbn=978-81-7371-254-8 |pages=449–466 |chapter-url=https://books.google.com/books?id=xTy_M3B5sf4C&pg=PA462 |access-date=15 April 2022 |language=en}}</ref><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 |pages=10 |doi=10.3390/biochem5020010 |doi-access=free |issn=2673-6411|pmc=12163724 }}</ref> | ||
A subunit is often named with a Greek or Roman letter, and the numbers of this type of subunit in a protein is indicated by a subscript.<ref name="Lesieur">{{cite book |last1=Lesieur |first1=Claire |title=Oligomerization of Chemical and Biological Compounds |date=18 June 2014 |publisher=Intech |location=Croatia |isbn=978-953-51-1617-2 |pages=240–241 |url=https://books.google.com/books?id=vjehDwAAQBAJ&dq=%22protein+subunit%22+oligomer&pg=PA240 |access-date=15 April 2022 |language=en}}</ref> For example, [[ATP synthase]] has a type of subunit called α. Three of these are present in the ATP synthase molecule, leading to the designation α<sub>3</sub>. Larger groups of subunits can also be specified, like α<sub>3</sub>β<sub>3</sub>-hexamer and c-ring.<ref name="Ahmad">{{cite journal |last1=Ahmad |first1=Zulfiqar |last2=Okafor |first2=Florence |last3=Azim |first3=Sofiya |last4=Laughlin |first4=Thomas F. |title=ATP Synthase: A Molecular Therapeutic Drug Target for Antimicrobial and Antitumor Peptides |journal=Current Medicinal Chemistry |date=2013 |volume=20 |issue=15 |pages=1956–1973 |doi=10.2174/0929867311320150003 |pmid=23432591 |pmc=4734648 |issn=0929-8673}}</ref> | A subunit is often named with a Greek or Roman letter, and the numbers of this type of subunit in a protein is indicated by a subscript.<ref name="Lesieur">{{cite book |last1=Lesieur |first1=Claire |title=Oligomerization of Chemical and Biological Compounds |date=18 June 2014 |publisher=Intech |location=Croatia |isbn=978-953-51-1617-2 |pages=240–241 |url=https://books.google.com/books?id=vjehDwAAQBAJ&dq=%22protein+subunit%22+oligomer&pg=PA240 |access-date=15 April 2022 |language=en}}</ref> For example, [[ATP synthase]] has a type of subunit called α. Three of these are present in the ATP synthase molecule, leading to the designation α<sub>3</sub>. Larger groups of subunits can also be specified, like α<sub>3</sub>β<sub>3</sub>-hexamer and c-ring.<ref name="Ahmad">{{cite journal |last1=Ahmad |first1=Zulfiqar |last2=Okafor |first2=Florence |last3=Azim |first3=Sofiya |last4=Laughlin |first4=Thomas F. |title=ATP Synthase: A Molecular Therapeutic Drug Target for Antimicrobial and Antitumor Peptides |journal=Current Medicinal Chemistry |date=2013 |volume=20 |issue=15 |pages=1956–1973 |doi=10.2174/0929867311320150003 |pmid=23432591 |pmc=4734648 |issn=0929-8673}}</ref> | ||
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== See also == | == See also == | ||
* [[Allostery]] | |||
* [[Cooperative binding|Cooperativity]] | |||
* [[Fusion protein]] | * [[Fusion protein]] | ||
* [[Monomer]] | |||
* [[Protein quaternary structure]] | |||
* [[Subunit vaccine]] | * [[Subunit vaccine]] | ||
==References== | ==References== | ||
Latest revision as of 12:29, 27 December 2025
In structural biology, a protein subunit is a polypeptide chain or single protein molecule that assembles (or "coassembles") with others to form a protein complex.[1][2][3] Large assemblies of proteins such as viruses often use a small number of types of protein subunits as building blocks.[4][5]
A subunit is often named with a Greek or Roman letter, and the numbers of this type of subunit in a protein is indicated by a subscript.[6] For example, ATP synthase has a type of subunit called α. Three of these are present in the ATP synthase molecule, leading to the designation α3. Larger groups of subunits can also be specified, like α3β3-hexamer and c-ring.[7]
Naturally occurring proteins that have a relatively small number of subunits are referred to as oligomeric.[8] For example, hemoglobin is a symmetrical arrangement of two identical α-globin subunits and two identical β-globin subunits.[3][9] Longer multimeric proteins such as microtubules and other cytoskeleton proteins may consist of very large numbers of subunits. For example, dynein is a multimeric protein complex involving two heavy chains (DHCs), two intermediate chains (ICs), two light-intermediate chains (LICs) and several light chains (LCs).[10]
The subunits of a protein complex may be identical, homologous or totally dissimilar and dedicated to disparate tasks.[1] In some protein assemblies, one subunit may be a "catalytic subunit" that enzymatically catalyzes a reaction, whereas a "regulatory subunit" will facilitate or inhibit the activity.[11] Although telomerase has telomerase reverse transcriptase as a catalytic subunit, regulation is accomplished by factors outside the protein.[12]
An enzyme composed of both regulatory and catalytic subunits when assembled is often referred to as a holoenzyme. For example, class I phosphoinositide 3-kinase is composed of a p110 catalytic subunit and a p85 regulatory subunit.[13] One subunit is made of one polypeptide chain. A polypeptide chain has one gene coding for it – meaning that a protein must have one gene for each unique subunit.
See also
References
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