Avidin: Difference between revisions
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<StructureSection load='2avi' size='350' side='right' scene='41/410356/Cv/4' caption='The avidin tetramer complex with biotin (PDB code [[2avi]])'> | <StructureSection load='2avi' size='350' side='right' scene='41/410356/Cv/4' caption='The avidin tetramer complex with biotin (PDB code [[2avi]])'> | ||
__TOC__ | |||
==Function== | |||
[[Avidin]] '''(Av)''' is a protein found in egg white which binds biotin (vitamin B7) with high affinity. This property makes it a powerful tool in various protein pull-down assays. Similar proteins are:<br /> | [[Avidin]] '''(Av)''' is a protein found in egg white which binds biotin (vitamin B7) with high affinity. This property makes it a powerful tool in various protein pull-down assays. Similar proteins are:<br /> | ||
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* '''Rhizavidin''' (RhiAv) from ''Rhizobium etli''<br /> | * '''Rhizavidin''' (RhiAv) from ''Rhizobium etli''<br /> | ||
* '''Xenavidin''' from frog<br /> | * '''Xenavidin''' from frog<br /> | ||
* '''Zebavidin''' from zebrafish<br /> | |||
* '''Tamavidin''' from fungi<br /> | * '''Tamavidin''' from fungi<br /> | ||
* '''Bradavidin''' from ''Bradyrhizobium japonicum''<br /> | * '''Bradavidin''' from ''Bradyrhizobium japonicum''<br /> | ||
* '''Hoefavidin''' from ''Hoeflea phototrophica''<br /> | * '''Hoefavidin''' from ''Hoeflea phototrophica''<br /> | ||
* '''Shwanavidin''' from ''Shewanella dentrifica''<br /> | * '''Shwanavidin''' from ''Shewanella dentrifica''<br /> | ||
* '''Wilavidin''' from ''Gammaproteobacteria bacterium'' forms biotin-binding hexameters<br /> | |||
* '''AVR2''' and '''AVR4''' are avidin-related proteins. | * '''AVR2''' and '''AVR4''' are avidin-related proteins. | ||
Avidin is one of the [[CBI Molecules]] being studied in the [http://www.umass.edu/cbi/ University of Massachusetts Amherst Chemistry-Biology Interface Program] at UMass Amherst and on display at the [http://www.molecularplayground.org/ Molecular Playground]. | Avidin is one of the [[CBI Molecules]] being studied in the [http://www.umass.edu/cbi/ University of Massachusetts Amherst Chemistry-Biology Interface Program] at UMass Amherst and on display at the [http://www.molecularplayground.org/ Molecular Playground]. | ||
<scene name='41/410356/Cv/ | <scene name='41/410356/Cv/15'>Avidin is a tetrameric protein</scene> what in different words means that if we could, we would see a protein with four regions that look identical one to the other. However, to isolate the four regions as a whole in order to show the protein three dimensional structure has been quite diffucult so far and we just can see the three dimensional structure for <scene name='41/410356/Cv/16'>two of those four units</scene>. <ref group="xtra">PMID:8506353</ref><ref group="xtra">PMID:8344421</ref> | ||
{{Clear}} | {{Clear}} | ||
The binding affinity of biotin for the avidin <scene name=' | The binding affinity of biotin for the avidin <scene name='41/410356/Cv/17'>receptors</scene> is very hight or in other words, the strength of the interations between the biotin and the avidin receptors is so strong that washing the biotin-avidin complex is not enough to remove the ligand from its pocket. This is not even possible by adding more biotin molecules to the system avidin-biotin. Once a biotin has bound a pocket in the avidin, it is almost imposible to remove it in a biological system! | ||
Each monomer is an eight-stranded antiparallel <scene name=' | Each monomer is an eight-stranded antiparallel <scene name='41/410356/Cv/18'>beta-barrel</scene>. Binding of biotin involves a highly stabilized network of polar and hydrophobic interactions. | ||
The presence of additional hydrophobic and hydrophilic groups in the binding site of avidin may account for its higher affinity constant. | The presence of additional hydrophobic and hydrophilic groups in the binding site of avidin may account for its higher affinity constant. | ||
Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer. These <scene name=' | Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer. These <scene name='41/410356/Cv/19'>sugars</scene> appear along with the biotin but outside of the biotin binding pockets. | ||
*<scene name='41/410356/Cv/20'>Biotin has bound a pocket in the avidin</scene>. | |||
See also:<br /> | See also:<br /> | ||
* [[Molecular Playground/Streptavidin]] | * [[Molecular Playground/Streptavidin]] | ||
* [[Streptavidin Binding Site]] | * [[Streptavidin Binding Site]] | ||
* [[Hila Cohen/Test Page]] | |||
* [[Molecular Playground/Biotin binding avidin]] | |||
==About this Structure== | ==About this Structure== | ||
[[2avi]] is a 2 chains structure of sequences from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2AVI OCA]. | [[2avi]] is a 2 chains structure of sequences from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2AVI OCA]. | ||
== 3D structures of Avidin == | |||
[[Avidin 3D structures]] | |||
</StructureSection> | </StructureSection> | ||
==Reference== | ==Reference== | ||