Avidin: Difference between revisions
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Avidin is a tetrameric protein 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 two of those four units. <ref group="xtra">PMID:8506353</ref><ref group="xtra">PMID:8344421</ref> | Avidin is a tetrameric protein 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 two of those four units. <ref group="xtra">PMID:8506353</ref><ref group="xtra">PMID:8344421</ref> | ||
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<applet load='2avi' size='300' frame='true' align='right' caption='Two monomers of the tetramer Avidin' /> | |||
The binding affinity of biotin for the avidin <scene name='Sandbox-test/Biotin_binding_avidin/1'>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 biologica system! | The binding affinity of biotin for the avidin <scene name='Sandbox-test/Biotin_binding_avidin/1'>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 biologica system! | ||
Each monomer is an eight-stranded antiparallel <scene name='Sandbox-test/Avidin_b-barrels/1'>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. | ||
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Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer. These <scene name='Sandbox-test/Ligands/1'>sugars</scene> appear along with the biotin but outside of the biotin binding pockets. | Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer. These <scene name='Sandbox-test/Ligands/1'>sugars</scene> appear along with the biotin but outside of the biotin binding pockets. | ||
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==About this Structure== | ==About this Structure== | ||
