Gammavidin – A novel member of the dimeric avidin family

The avidin family is well known for its extremely high affinity towards biotin, with a Kd of ~10^-15M. The first discovered avidins exhibits a tetrameric assembly and contains 4 binding site to biotin (one per each monomer). In addition to its high affinity towards biotin, high thermostability made the proteins a widely used biotechnological tool serving as specific molecular glue and many other applications. Their large size and 4 different binding sites could result in unwanted crosslinking, steric disturbance and other technological challenges, thus minimization of the system could diversify the applications utilizing avidins. Approximately a decade ago a new group in the avidins was discovered, which introduced a dimeric quaternary structure while maintaining the high affinity towards biotin. The first unique avidin dimer to be discovered was the rhizavidin, and since then several more dimeric avidins were identified using BLAST.

A new dimeric member of the family, from the Gammaproteobacteria bacterium genome, was discovered and denoted gammavidin. In the study, we found that gammavidin exhibits a somewhat lower affinity towards 2-imminobiotin then other avidin family members. The crystal structure reveals intriguing new features that might explain the lower affinity. Additional biochemical research and structural analyses are carried out in order to find new ways to utilize this interesting novel protein and extend the avidin biotin toolbox.