Protein subunit
Instructural biology,aprotein subunitis apolypeptide chainor singleproteinmolecule that assembles (or "coassembles") with others to form aprotein complex.[1][2][3] Large assemblies of proteins such asvirusesoften use a small number of types of protein subunits as building blocks.[4]
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.[5]For example,ATP synthasehas 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.[6]
Naturally occurring proteins that have a relatively small number of subunits are referred to asoligomeric.[7]For example,hemoglobinis a symmetrical arrangement of two identical α-globin subunits and two identical β-globin subunits.[3][8]Longermultimericproteins such asmicrotubulesand othercytoskeletonproteins may consist of very large numbers of subunits. For example,dyneinis a multimeric protein complex involving two heavy chains (DHCs), two intermediate chains (ICs), two light-intermediate chains (LICs) and several light chains (LCs).[9]
The subunits of a protein complex may be identical,homologousor totally dissimilar and dedicated to disparate tasks.[1] In some protein assemblies, one subunit may be a "catalytic subunit" that enzymaticallycatalyzesa reaction, whereas a "regulatory subunit" will facilitate or inhibit the activity.[10]Althoughtelomerasehastelomerase reverse transcriptaseas a catalytic subunit, regulation is accomplished by factors outside the protein.[11]
An enzyme composed of both regulatory and catalytic subunits when assembled is often referred to as aholoenzyme.For example,class I phosphoinositide 3-kinaseis composed of a p110 catalytic subunit and a p85 regulatory subunit.[12]One subunit is made of onepolypeptidechain. A polypeptide chain has onegenecoding for it – meaning that a protein must have one gene for each unique subunit.
See also[edit]
References[edit]
- ^abStoker, H. Stephen (1 January 2015).General, Organic, and Biological Chemistry(7th ed.). Boston, MA: Cengage Learning. pp. 709–710.ISBN978-1-305-68618-2.Retrieved15 April2022.
- ^Smith, Michael B. (27 April 2020).Biochemistry: An Organic Chemistry Approach.Boca Raton: CRC Press. pp. 269–270.ISBN978-1-351-25807-4.Retrieved15 April2022.
- ^abAlberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter (2002).The Shape and Structure of Proteins.New York: Garland Science.Retrieved15 April2022.
- ^Kumar, A.; Evarsson, A.; Hol, W. G. J. (1999)."Multi-protein assemblies with point group symmetry".In Vijayan, M.; Yathindra, N.; Kolaskar, A. S. (eds.).Perspectives in Structural Biology: A Volume in Honour of G.N. Ramachandran.Hyderabad, India: Universities Press. pp. 449–466.ISBN978-81-7371-254-8.Retrieved15 April2022.
- ^Lesieur, Claire (18 June 2014).Oligomerization of Chemical and Biological Compounds.Croatia: Intech. pp. 240–241.ISBN978-953-51-1617-2.Retrieved15 April2022.
- ^Ahmad, Zulfiqar; Okafor, Florence; Azim, Sofiya; Laughlin, Thomas F. (2013)."ATP Synthase: A Molecular Therapeutic Drug Target for Antimicrobial and Antitumor Peptides".Current Medicinal Chemistry.20(15): 1956–1973.doi:10.2174/0929867311320150003.ISSN0929-8673.PMC4734648.PMID23432591.
- ^Jenkins, A. D.; Kratochvíl, P.; Stepto, R. F. T.; Suter, U. W. (1996)."Glossary of basic terms in polymer science (IUPAC Recommendations 1996)".Pure and Applied Chemistry.68(12): 2287–2311.doi:10.1351/pac199668122287.Quote:Oligomer molecule: A molecule of intermediate relative molecular mass, the structure of which essentially comprises a small plurality of units derived, actually or conceptually, from molecules of lower relative molecular mass.
- ^Liu, Shijie (7 April 2020).Bioprocess Engineering: Kinetics, Sustainability, and Reactor Design.Elsevier. p. 358.ISBN978-0-12-822383-3.Retrieved15 April2022.
- ^Dharan, Adarsh; Campbell, Edward M. (31 July 2018)."Role of Microtubules and Microtubule-Associated Proteins in HIV-1 Infection".Journal of Virology.92(16): e00085–18.doi:10.1128/JVI.00085-18.ISSN0022-538X.PMC6069196.PMID29899089.
- ^Søberg, Kristoffer; Skålhegg, Bjørn Steen (12 September 2018)."The Molecular Basis for Specificity at the Level of the Protein Kinase a Catalytic Subunit".Frontiers in Endocrinology.9:538.doi:10.3389/fendo.2018.00538.ISSN1664-2392.PMC6143667.PMID30258407.
- ^Daniel M, Peek GW, Tollefsbol TO (2012)."Regulation of the human catalytic subunit of telomerase (hTERT)".Gene.498(2): 135–46.doi:10.1016/j.gene.2012.01.095.PMC3312932.PMID22381618.
- ^Carpenter CL, Duckworth BC, Auger KR, Cohen B, Schaffhausen BS, Cantley LC (November 1990)."Purification and characterization of phosphoinositide 3-kinase from rat liver".J. Biol. Chem.265(32): 19704–11.doi:10.1016/S0021-9258(17)45429-9.PMID2174051.