Oleosin

{{Infobox protein family | Symbol = Oleosin | Name = Oleosin | image = | width = | caption = | Pfam = PF01277 | Pfam_clan = CL0111 | InterPro = IPR000136 | SMART = | PROSITE = PDOC00639 | MEROPS = | SCOP = | TCDB = | OPM family = | OPM protein = | CAZy = | CDD = }} '''Oleosins''' are structural proteins found in vascular plant oil bodies and in plant cells. Oil bodies are not considered organelles because they have a single layer membrane and lack the pre-requisite double layer membrane in order to be considered an organelle. They are found in plant parts with high oil content that undergo extreme desiccation as part of their maturation process, and help stabilize the bodies.<ref>{{cite journal |last=Hsieh |first=Kai |author2=Anthony H.C. Huang| title= Lipid-rich tapetosomes in ''Brassica'' tapetum are composed of oleosin-coated oil droplets and vesicles, both assembled in and then detached from the endoplasmic reticulum|journal=The Plant Journal| volume=43|date=September 2005| issue=6| pages=889–99|pmid=16146527|doi=10.1111/j.1365-313X.2005.02502.x |doi-access=free}}</ref>

== Components == Oleosins are proteins of 16 kDa to 24 kDa and are composed of three domains: an N-terminal hydrophilic region of variable length (from 30 to 60 residues); a central hydrophobic domain of about 70 residues and a C-terminal amphipathic region of variable length (from 60 to 100 residues). The central hydrophobic domain is proposed to be made up of beta-strand structure and to interact with the lipids. It is the only domain whose sequence is conserved.<ref name="pmid1639802">{{cite journal |vauthors=Tzen JT, Lie GC, Huang AH | title = Characterization of the charged components and their topology on the surface of plant seed oil bodies | journal = J. Biol. Chem. | volume = 267 | issue = 22 | pages = 15626–34 |date=August 1992 | doi = 10.1016/S0021-9258(19)49582-3 | pmid = 1639802 | doi-access = free }}</ref> Models show oleosins having a hairpin-like hydrophobic shape that is inserted inside the triacylglyceride (TAG), while the hydrophilic parts are left outside oil bodies.<ref>{{Cite web |url=https://www.usask.ca/agriculture/plantsci/classes/plsc416/projects_2002/weightman/416%20webpage/oleosin.html |title=oleosin |access-date=2017-08-18 |archive-date=2009-01-29 |archive-url=https://web.archive.org/web/20090129191649/http://www.usask.ca/agriculture/plantsci/classes/plsc416/projects_2002/weightman/416%20webpage/oleosin.html |url-status=dead }}</ref>

Oleosins have been found on oil bodies of seeds, tapetum cells, and pollen but not fruits. Instead of a stabilizer of oil bodies, oleosins are believed to be involved in water-uptaking of pollen on stigma.

==Allergic reactions== Allergic reactions to oleosins from hazelnut, peanut and sesame oils have been confirmed, ranging from contact dermatitis to anaphylactic shock.<ref name="Jappe2017">{{cite journal |vauthors=Jappe U, Schwager C |title=Relevance of Lipophilic Allergens in Food Allergy Diagnosis |journal=Curr Allergy Asthma Rep |volume=17 |issue=9 |article-number=61 |date=August 2017 |pmid=28795292 |doi=10.1007/s11882-017-0731-0 |s2cid=562068 |url=}}</ref><ref name="Zuid2014">{{cite journal |vauthors=Zuidmeer-Jongejan L, Fernández-Rivas M, Winter MG, Akkerdaas JH, Summers C, Lebens A, Knulst AC, Schilte P, Briza P, Gadermaier G, van Ree R |display-authors=5 |title=Oil body-associated hazelnut allergens including oleosins are underrepresented in diagnostic extracts but associated with severe symptoms |journal=Clin Transl Allergy |volume=4 |issue=1 |pages=4 |date=February 2014 |pmid=24484687 |pmc=4015814 |doi=10.1186/2045-7022-4-4 |url= |doi-access=free }}</ref><ref name="Alonzi2011">{{cite journal |vauthors=Alonzi C, Campi P, Gaeta F, Pineda F, Romano A |title=Diagnosing IgE-mediated hypersensitivity to sesame by an immediate-reading "contact test" with sesame oil |journal=J Allergy Clin Immunol |volume=127 |issue=6 |pages=1627–29 |date=June 2011 |pmid=21377720 |doi=10.1016/j.jaci.2011.01.050 |url=}}</ref><ref name="Leduc2006">{{cite journal |vauthors=Leduc V, Moneret-Vautrin DA, Tzen JT, Morisset M, Guerin L, Kanny G |title=Identification of oleosins as major allergens in sesame seed allergic patients |journal=Allergy |volume=61 |issue=3 |pages=349–56 |date=March 2006 |pmid=16436145 |doi=10.1111/j.1398-9995.2006.01013.x |s2cid=33598622 |url=}}</ref><ref name="Kany1996">{{cite journal |vauthors=Kanny G, De Hauteclocque C, Moneret-Vautrin DA |title=Sesame seed and sesame seed oil contain masked allergens of growing importance |journal=Allergy |volume=51 |issue=12 |pages=952–7 |date=December 1996 |pmid=9020427 |doi= 10.1111/j.1398-9995.1996.tb02141.x|url=}}</ref> These oil body associated proteins are at ~14 and ~17 kDa, named, respectively, Ses i 5 and Ses i 4.<ref name="Zuid2014"/><ref name="Leduc2006"/> Commercial-grade peanut oil is often highly refined, which makes it safe for most peanut allergic individuals. In contrast, commercial-grade sesame oil is typically an unrefined product with a measurably higher protein content.<ref name="Alonzi2011"/> In addition to being a food ingredient, sesame oil can be present in drug products, dietary supplements and topically applied cosmetics.<ref name="Kany1996"/>

==Usage== Oleosins provide an easy way of purifying proteins which have been produced recombinantly in plants. If the protein is made as a fusion protein with oleosin and a protease recognition site is incorporated between them, the fusion protein will sit in the membrane of the oil body, which can be easily isolated by centrifugation. The oil droplets can then be mixed with aqueous medium again, and oleosin cleaved from the protein of interest. Centrifugation will cause two phases to separate again, and the aqueous medium now contains the purified protein.

==References== <references/>

Category:Protein families Category:Plant cells Category:Plant proteins