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Avidin is a homotetrameric protein known for its high binding affinity and specificity for biotin which gives it great functionality in many biotech applications. Prior research on the bacterial analog, streptavidin found cooperative allosterism exhibited in the binding process. This research was aimed at investigating whether this same cooperative allosterism accompanies the binding of biotin to avidin. This work measured intrinsic tryptophan fluorescence as biotin was titrated into avidin. A blueshift in the wavelength of maximum fluorescence as well as quenching of the overall fluorescence intensity, similar to the streptavidin was observed. The saturation point for 335 nm emission (tryptophans in more hydrophobic environments) was lower than the 4:1 stoichiometric ratio exhibited by the 350 nm emission (tryptophans in more hydrophilic environments). This suggest biotin binding to avidin exemplifies cooperative allosterism similar to that of streptavidin. Additional fluorescence based parameters were also examined and will be described relative to those for streptavidin as well.
Murphy, Alycia, "Cooperative Allosterism in Avidin and Streptavidin Upon Biotin Binding as Observed by Changes in Intrinsic Fluorescence" (2022). Celebration of Scholarship 2022. 4.