Molecular Playground/Biotin binding avidin
One of the CBI Molecules being studied in the University of Massachusetts Amherst Chemistry-Biology Interface Program at UMass Amherst and on display at the Molecular Playground.
Tetramer of Avidin Binding the Biotin Ligands
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.
The binding affinity of biotin for the avidin is very hight, 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 presence of additional hydrophobic and hydrophilic groups in the binding site of avidin may account for its higher affinity constant or binding strength.
Unexpectedly, a residual N-acetylglucosamine moiety was detected in the deglycosylated avidin monomer. These appear along with the biotin but outside of the biotin binding pockets.
Avidin and modified biotin are been used by the Thayumanavan Reserach Group to learn more about micellar disassembly.