Avidin
| Avidin ( Gallus gallus ) | ||
|---|---|---|
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| Ribbon model of an avidin dimer, with bound biotin as a cap, according to PDB 1AVD | ||
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Existing structural data: s. UniProt |
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| Mass / length primary structure | 128 amino acids | |
| Secondary to quaternary structure | Homotetramer | |
| Identifier | ||
| Gene name (s) | AVD | |
| External IDs | ||
Avidin is a glycoprotein in the egg white of bird eggs, which can bind biotin (vitamin B7). The biological function of avidin is not known in detail. It is believed, however, that the avidin in egg white represents a defense mechanism and has an inhibitory effect on bacterial growth. In hen's eggs , it makes up about 0.05 percent of the egg white protein.
It is a tetrameric protein that can bind four biotin molecules. The ability of avidin to bind biotin also means that biotin cannot be absorbed in the gastrointestinal tract if you eat a lot of raw eggs. Avidin reduces the availability of both the diet and the biotin produced by the intestinal flora . In this way, by adding avidin or raw egg white to normal food, a biotin deficiency can be produced experimentally.
structure
The primary structure of the monomer, i.e. each of the four identical subunits, consists of 128 amino acids , the tetramer has a total molecular mass of 66 kDa .
Homologues
Streptavidin is a bacterial avidin from Streptomyces , which also binds biotin, albeit slightly weaker than avidin. However, because bacterial streptavidin is not a glycoprotein and therefore has fewer unspecific bonds, it is the preferred choice in biochemistry.
discovery
In 1940 it was observed that chicks that were given raw egg white were suffering from a lack of biotin. In the same year Esmond Emerson Snell was the first to succeed in isolating the corresponding protein. He named it avidin after its ability to combine "greedily" ("avid") with biotin.
Green biotechnology
With the avidin maize, a transgenic maize was developed via green genetic engineering which is able to express avidin in concentrations above 100 ppm . Due to the biotin binding, this protects the maize against pest infestation, especially during storage, since the biotin deficiency that is caused is toxic to harmful insects. Maize was not poisonous to mice fed the maize for 21 days. This is intended to reduce crop failures due to insect infestation during storage, especially in tropical countries. In addition, experiments were carried out on how the synergy effects of Bt and avidin maize can be used as insect protection.
Web links
- RCSB Protein Data Bank: 1VYO Structure Summary (Molecule Visualization)
Individual evidence
- ↑ UniProt P02701
- ↑ David L. Nelson, Michael M. Cox, Albert L Lehninger: Principles of Biochemistry. 5th edition. WH Freeman, New York 2008, ISBN 978-0-7167-7108-1 .
- ↑ Gerald Rimbach, Jennifer Nagursky, Helmut F. Erbersdobler: Food and goods knowledge for beginners . Springer-Verlag, 2015, ISBN 978-3-662-46280-5 , pp. 59 ( limited preview in Google Book search).
- ↑ invitrogen: Molecular probes: Handbook of fluorescent probes and research chemicals. 7th edition. Eugene, Or., Molecular Probes, 1999, ISBN 0-9652240-5-8 page on avidin
- ^ Nicole Kresge, Robert D. Simoni, Robert L. Hill: The Discovery of Avidin by Esmond E. Snell. In: The Journal of Biological Chemistry.
- ^ KJ Kramer, TD Morgan, JE Throne, FE Dowell, M. Bailey, JA Howard: Transgenic avidin maize is resistant to storage insect pests. In: Nature Biotechnology . 18 (6), 2000, pp. 670-674. PMID 10835608 .
- ↑ YC Zhu, JJ Adamczyk Jr, S. West: Avidin, a potential biopesticide and synergist to Bacillus thuringiensis toxins against field crop insects. In: Journal of Economic Entomology. 98 (5), 2005, pp. 1566-1571. PMID 16334325 .