Avidin

{{Short description|Type of protein}} {{Infobox protein family | Symbol = Avidin | Name = Avidin family | image = Tetramer.png | width = | caption = Tetrameric structure of streptavidin with 2 bound biotins | Pfam = PF01382 | Pfam_clan = | InterPro = IPR005468 | SMART = | PROSITE = PDOC00499 | MEROPS = | SCOP = 1slf | CATH = 1slf | TCDB = | OPM family = | OPM protein = | CAZy = | CDD = }} thumb|'''Biotin''' - Avidin can bind up to four molecules of biotin simultaneously with a high degree of affinity and specificity '''Avidin''' is a tetrameric biotin-binding protein produced in the oviducts of birds, reptiles and amphibians and deposited in the whites of their eggs. Dimeric members of the avidin family are also found in some bacteria.<ref name = "Helppolainen_2007" /> In chicken egg white, avidin makes up approximately 0.05% of total protein (approximately 1800 μg per egg). The tetrameric protein contains four identical subunits (homotetramer), each of which can bind to biotin (Vitamin B7, vitamin H) with a high degree of affinity and specificity. The dissociation constant of the avidin-biotin complex is measured to be ''K''D ≈ 10−15 M, making it one of the strongest known non-covalent bonds.<ref name = "Green_1963" />

In its tetrameric form, avidin is estimated to be 66–69 kDa in size.<ref name = "Korpela_1984" /> 10% of the molecular weight is contributed by carbohydrate, composed of four to five mannose and three N-acetylglucosamine residues<ref name = "Green_1975" /> The carbohydrate moieties of avidin contain at least three unique oligosaccharide structural types that are similar in structure and composition.<ref name = "Bruch_1982" />

Functional avidin is found in raw egg, but depending on the amount of heat it is exposed to during cooking, the quantity of molecules available for binding biotin can change. The natural function of avidin in eggs is not known, although it has been postulated to be made in the oviduct as a bacterial growth inhibitor, by binding biotin helpful for bacterial growth. As evidence for this, streptavidin, a related protein with equal biotin affinity and a very similar binding site, is made by certain strains of ''Streptomyces'' bacteria, and is thought to serve to inhibit the growth of competing bacteria, in the manner of an antibiotic.<ref name = "Hendrickson_1989" />

A non-glycosylated form of avidin has been isolated from commercially prepared product; however, it is not conclusive as to whether the non-glycosylated form occurs naturally or is a product of the manufacturing process.<ref name = "Hiller_1987" />

== Discovery == thumb|A raw egg yolk surrounded by the egg white. Avidin was first isolated from raw chicken egg white by Esmond Emerson Snell Avidin was discovered by Esmond Emerson Snell (1914–2003). This discovery began with the observation that chicks on a diet of raw egg white were deficient in biotin, despite availability of the vitamin in their diet.<ref name="Eakin_1940" /> It was concluded that a component of the egg-white was sequestering biotin<ref name="Eakin_1940"/> which Snell verified ''in vitro'' using a yeast assay.<ref name = "Snell_1940" /> Snell later isolated the component of egg white responsible for biotin binding, and, in collaboration with Paul György, confirmed that the isolated egg protein was the cause of biotin deficiency or “egg white injury”.<ref name="György_1941" /> At the time the protein had been tentatively named avidalbumin (literally, hungry albumin) by researchers at the University of Texas.<ref name="György_1941"/> The name of the protein was later revised to "avidin" based on its affinity for biotin (avid + biotin).<ref name = "Kresge_2004" />

== Applications== {{Infobox nonhuman protein |Name=Avidin |UniProt=P02701 |Organism=Chicken |Symbol=AVD |footnotes = Unless otherwise specified, "avidin" the biomedical reagent is chicken avidin. }} Research in the 1970s helped establish the avidin-biotin system as a powerful tool in biological sciences. Aware of the strength and specificity of the avidin-biotin complex, researchers began to exploit chicken avidin and streptavidin as probes and affinity matrices in numerous research projects.<ref name = "Hofmann_1976" /><ref name = "Bayer_1976" /><ref name = "Angerer_1976" /><ref name = "Heggeness_1977" /> Soon after, researchers Bayer and Wilchek developed new methods and reagents to biotinylate antibodies and other biomolecules,<ref name = "Bayer_1985" /><ref name = "Wilchek_1986" /> allowing the transfer of the avidin-biotin system to a range of biotechnological applications. Today, avidin is used in a variety of applications ranging from research and diagnostics to medical devices and pharmaceuticals.

Avidin's affinity for biotin is exploited in wide-ranging biochemical assays, including western blot, ELISA, ELISPOT and pull-down assays. In some cases the use of biotinylated antibodies has allowed the replacement of radioiodine labeled antibodies in radioimmunoassay systems, to give an assay system which is not radioactive.{{Citation needed|date=May 2016}}

Avidin immobilized onto solid supports is also used as purification media to capture biotin-labelled protein or nucleic acid molecules. For example, cell surface proteins can be specifically labelled with membrane impermeable biotin reagent, then specifically captured using an avidin-based support.{{Citation needed|date=May 2016}}

== Modified forms == As a basically charged glycoprotein, avidin exhibits non-specific binding in some applications. Neutralite avidin, a deglycosylated avidin with modified arginines, exhibits a more neutral isoelectric point (pI) and is available as an alternative to native avidin, whenever problems of non-specific binding arise. Deglycosylated, neutral forms of chicken avidin are available through Sigma-Aldrich (Extravidin), Thermo Scientific (NeutrAvidin), Invitrogen (NeutrAvidin), and e-Proteins (NeutraLite).

Given the strength of the avidin-biotin bond, dissociation of the avidin-biotin complex requires extreme conditions that cause protein denaturation. The non-reversible nature of the avidin-biotin complex can limit avidin's application in affinity chromatography applications where release of the captured ligand is desirable. Researchers have created an avidin with reversible binding characteristics through nitration or iodination of the binding site tyrosine.<ref name="Morag_1976" /> The modified avidin exhibits strong biotin binding characteristics at pH 4 and releases biotin at a pH of 10 or higher.<ref name="Morag_1976"/> A monomeric form of avidin with a reduced affinity for biotin is also employed in many commercially available affinity resins. The monomeric avidin is created by treatment of immobilized native avidin with urea or guanidine HCl (6–8 M), giving it a lower dissociation ''K''D ≈ 10−7M.<ref name = "Kohanski_1990" /> This allows elution from the avidin matrix to occur under milder, non-denaturing conditions, using low concentrations of biotin or low pH conditions. For a single high affinity biotin binding site without crosslinking, a monovalent version of avidin's distant relative, streptavidin, may be used.<ref name = "Howarth_2006" />

==Blocking of biotin binding ==

The thermal stability and biotin binding activity of avidin are of both practical and theoretical interest to researchers, as avidin's stability is unusually high and avidin is an antinutrient in human food.<ref name = "Durance_1992" /> A 1966 study published in ''Biochemical and Biophysical Research Communications'' found that the structure of avidin remains stable at temperatures below {{convert|70|°C|°F}}. Above {{convert|70|°C|°F}}, avidin's structure is rapidly disrupted and by {{convert|85|°C|°F}}, extensive loss of structure and loss of ability to bind biotin is found.<ref name = "Pritchard_1966" /> A 1991 assay for the ''Journal of Food Science'' detected substantial avidin activity in cooked egg white: "mean residual avidin activity in fried, poached and boiled (2 min) egg white was 33, 71 and 40% of the activity in raw egg white." The assay surmised that cooking times were not sufficient to adequately heat all cold spot areas within the egg white. Complete inactivation of avidin's biotin binding capacity required boiling for over 4 minutes.<ref name = "Durance_1991" />

A 1992 study found that thermal inactivation of the biotin binding activity of avidin was described by D121 °C = 25 min and z = 33 °C. This study disagreed with prior assumptions "that the binding site of avidin is destroyed on heat denaturation".<ref name = "Durance_1992" />

The biotin-binding properties of avidin were exploited during the development of idrabiotaparinux, a long-acting low molecular weight heparin used in the treatment of venous thrombosis. Due to the long-acting nature of idraparinux, concerns were made about the clinical management of bleeding complications. By adding a biotin moiety to the idraparinux molecule, idrabiotaparinux was formed; its anticoagulant activity in the setting of a bleeding event can be reversed through an intravenous infusion of avidin.<ref name = "Büller_2012" />

== See also == *Streptavidin *Biotinylation

== References == {{reflist|32em|refs =

<ref name = "Angerer_1976">{{cite journal | vauthors = Angerer L, Davidson N, Murphy W, Lynch D, Attardi G | title = An electron microscope study of the relative positions of the 4S and ribosomal RNA genes in HeLa cells mitochondrial DNA | journal = Cell | volume = 9 | issue = 1 | pages = 81–90 | date = September 1976 | pmid = 975242 | doi = 10.1016/0092-8674(76)90054-4 | s2cid = 54340885 }}</ref>

<ref name = "Bayer_1976">{{cite journal | vauthors = Bayer EA, Skutelsky E, Wynne D, Wilchek M | title = Preparation of ferritin-avidin conjugates by reductive alkylation for use in electron microscopic cytochemistry | journal = The Journal of Histochemistry and Cytochemistry | volume = 24 | issue = 8 | pages = 933–9 | date = August 1976 | pmid = 182877 | doi = 10.1177/24.8.182877 | doi-access = free }}</ref>

<ref name = "Bayer_1985">{{cite journal | vauthors = Bayer EA, Zalis MG, Wilchek M | title = 3-(N-Maleimido-propionyl)biocytin: a versatile thiol-specific biotinylating reagent | journal = Analytical Biochemistry | volume = 149 | issue = 2 | pages = 529–36 | date = September 1985 | pmid = 3935007 | doi = 10.1016/0003-2697(85)90609-8 | doi-access = free }}</ref>

<ref name = "Bruch_1982">{{cite journal | vauthors = Bruch RC, White HB | title = Compositional and structural heterogeneity of avidin glycopeptides | journal = Biochemistry | volume = 21 | issue = 21 | pages = 5334–41 | date = October 1982 | pmid = 6816268 | doi = 10.1021/bi00264a033 }}</ref>

<ref name = "Büller_2012">{{cite journal | vauthors = Büller HR, Gallus AS, Pillion G, Prins MH, Raskob GE | title = Enoxaparin followed by once-weekly idrabiotaparinux versus enoxaparin plus warfarin for patients with acute symptomatic pulmonary embolism: a randomised, double-blind, double-dummy, non-inferiority trial | journal = Lancet | volume = 379 | issue = 9811 | pages = 123–9 | date = January 2012 | pmid = 22130488 | doi = 10.1016/S0140-6736(11)61505-5 | s2cid = 205964156 }}</ref>

<ref name = "Durance_1992">{{cite journal |doi=10.1016/0963-9969(92)90148-X |title=Kinetics of thermal inactivation of avidin |year=1992 | vauthors =Durance TD, Wong NS |journal=Food Research International |volume=25 |issue=2 |pages=89–92}}</ref>

<ref name = "Durance_1991">{{cite journal |doi=10.1111/j.1365-2621.1991.tb05361.x |title=Residual Avid in Activity in Cooked Egg White Assayed with Improved Sensitivity |year=1991 | vauthors = Durance TD |journal=Journal of Food Science |volume=56 |issue=3 |pages=707–9}}</ref>

<ref name = "Eakin_1940">{{cite journal | vauthors = Eakin RE, McKinley WA, Williams RJ | title = Egg-White Injury in Chicks and ITS Relationship to a Deficiency of Vitamin H (Biotin) | journal = Science | volume = 92 | issue = 2384 | pages = 224–5 | date = September 1940 | pmid = 17743857 | doi = 10.1126/science.92.2384.224 | bibcode = 1940Sci....92..224E }}</ref>

<ref name = "György_1941">{{cite journal | vauthors = György P, Rose CS, Eakin RE, Snell EE, Williams RJ | title = Egg-White Injury as the Result of Nonabsorption or Inactivation of Biotin | journal = Science | volume = 93 | issue = 2420 | pages = 477–8 | date = May 1941 | pmid = 17757050 | doi = 10.1126/science.93.2420.477 | bibcode = 1941Sci....93..477G }} </ref>

<ref name = "Green_1963">{{cite journal | vauthors = Green NM | title = Avidin. 1. The Use of (14-C)Biotin for Kinetic Studies and for Assay | journal = The Biochemical Journal | volume = 89 | issue = 3 | pages = 585–91 | date = December 1963 | pmid = 14101979 | pmc = 1202466 | doi = 10.1042/bj0890585 }}</ref>

<ref name = "Green_1975">{{cite journal | vauthors = Green NM | title = Avidin | journal = Advances in Protein Chemistry | volume = 29 | pages = 85–133 | year = 1975 | pmid = 237414 | doi = 10.1016/S0065-3233(08)60411-8 | isbn = 978-0-12-034229-7 | veditors = Anfinsen CB, Edsall JT, Richards FM | url = https://books.google.com/books?id=sMgpDLCl2z8C&pg=PA85 | url-access = registration }}</ref>

<ref name = "Heggeness_1977">{{cite journal | vauthors = Heggeness MH, Ash JF | title = Use of the avidin-biotin complex for the localization of actin and myosin with fluorescence microscopy | journal = The Journal of Cell Biology | volume = 73 | issue = 3 | pages = 783–8 | date = June 1977 | pmid = 326797 | pmc = 2111432 | doi = 10.1083/jcb.73.3.783 }}</ref>

<ref name = "Helppolainen_2007">{{cite journal | vauthors = Helppolainen SH, Nurminen KP, Määttä JA, Halling KK, Slotte JP, Huhtala T, Liimatainen T, Ylä-Herttuala S, Airenne KJ, Närvänen A, Jänis J, Vainiotalo P, Valjakka J, Kulomaa MS, Nordlund HR | display-authors = 6 | title = Rhizavidin from Rhizobium etli: the first natural dimer in the avidin protein family | journal = The Biochemical Journal | volume = 405 | issue = 3 | pages = 397–405 | date = August 2007 | pmid = 17447892 | pmc = 2267316 | doi = 10.1042/BJ20070076 }}</ref>

<ref name = "Hendrickson_1989">{{cite journal | vauthors = Hendrickson WA, Pähler A, Smith JL, Satow Y, Merritt EA, Phizackerley RP | title = Crystal structure of core streptavidin determined from multiwavelength anomalous diffraction of synchrotron radiation | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 86 | issue = 7 | pages = 2190–4 | date = April 1989 | pmid = 2928324 | pmc = 286877 | doi = 10.1073/pnas.86.7.2190 | bibcode = 1989PNAS...86.2190H | jstor = 33443 | doi-access = free }}</ref>

<ref name = "Hiller_1987">{{cite journal | vauthors = Hiller Y, Gershoni JM, Bayer EA, Wilchek M | title = Biotin binding to avidin. Oligosaccharide side chain not required for ligand association | journal = The Biochemical Journal | volume = 248 | issue = 1 | pages = 167–71 | date = November 1987 | pmid = 3435435 | pmc = 1148514 | doi = 10.1042/bj2480167 }}</ref>

<ref name = "Hofmann_1976">{{cite journal | vauthors = Hofmann K, Kiso Y | title = An approach to the targeted attachment of peptides and proteins to solid supports | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 73 | issue = 10 | pages = 3516–8 | date = October 1976 | pmid = 185617 | pmc = 431147 | doi = 10.1073/pnas.73.10.3516 | bibcode = 1976PNAS...73.3516H | jstor = 66631 | doi-access = free }}</ref>

<ref name = "Howarth_2006">{{cite journal | vauthors = Howarth M, Chinnapen DJ, Gerrow K, Dorrestein PC, Grandy MR, Kelleher NL, El-Husseini A, Ting AY | display-authors = 6 | title = A monovalent streptavidin with a single femtomolar biotin binding site | journal = Nature Methods | volume = 3 | issue = 4 | pages = 267–73 | date = April 2006 | pmid = 16554831 | pmc = 2576293 | doi = 10.1038/nmeth861 }}</ref>

<ref name = "Kohanski_1990">{{cite book | vauthors = Kohanski RA, Lane MD | title = Monovalent avidin affinity columns | series = Methods in Enzymology | volume = 184 | pages = 194–200 | year = 1990 | pmid = 2388570 | doi = 10.1016/0076-6879(90)84274-K | isbn = 978-0-12-182085-5 }}</ref>

<ref name = "Korpela_1984">{{cite journal | vauthors = Korpela J | title = Avidin, a high affinity biotin-binding protein, as a tool and subject of biological research | journal = Medical Biology | volume = 62 | issue = 1 | pages = 5–26 | year = 1984 | pmid = 6379329 }}</ref>

<ref name = "Kresge_2004">{{cite journal | vauthors = Kresge N, Simoni RD, Hill RL |year=2004 |title=The Discovery of Avidin by Esmond E. Snell |journal=The Journal of Biological Chemistry |volume=279 |issue=41 |pages=e5–e6 |doi=10.1016/S0021-9258(20)77095-X |url=http://www.jbc.org/content/279/41/e5.full |doi-access=free }}</ref>

<ref name = "Morag_1976">{{cite journal | vauthors = Morag E, Bayer EA, Wilchek M | title = Reversibility of biotin-binding by selective modification of tyrosine in avidin | journal = The Biochemical Journal | volume = 316 | issue = 1 | pages = 193–9 | date = May 1996 | pmid = 8645205 | pmc = 1217322 | doi = 10.1042/bj3160193 }}</ref>

<ref name = "Pritchard_1966">{{cite journal | vauthors = Pritchard AB, McCormick DB, Wright LD |doi=10.1016/0006-291X(66)90623-1 |title=Optical rotatory dispersion studies of the heat denaturation of avidin and the avidin-biotin complex |year=1966 |journal=Biochemical and Biophysical Research Communications |volume=25 |issue=5 |pages=524–8}}</ref>

<ref name = "Snell_1940">{{cite journal |doi=10.1021/ja01858a052 |year=1940 | vauthors = Snell EE, Eakin RE, Williams RJ |title=A Quantitative Test for Biotin and Observations Regarding its Occurrence and Properties |journal=Journal of the American Chemical Society |volume=62 |pages=175–8}}</ref>

<ref name = "Wilchek_1986">{{cite journal | vauthors = Wilchek M, Ben-Hur H, Bayer EA | title = p-Diazobenzoyl biocytin--a new biotinylating reagent for the labeling of tyrosines and histidines in proteins | journal = Biochemical and Biophysical Research Communications | volume = 138 | issue = 2 | pages = 872–9 | date = July 1986 | pmid = 3741438 | doi = 10.1016/S0006-291X(86)80577-0 }}</ref>

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== External links == * [http://www.ebi.ac.uk/pdbe-apps/quips?story=avidin Egg-stremely useful interaction]{{Dead link|date=November 2019}}—Structure article at the Protein Data Bank

Category:Avian proteins Category:Glycoproteins