Characterization of His-tagged, R6K-encoded pi protein variants.

The pi protein of plasmid R6K is a multifunctional replication (Rep) protein, its different activities attributable, in part, to different oligomeric states: monomers and dimers. We have previously shown that His-tagged variants of the protein can exhibit alterations in dimer stability. Herein, we examined the functional properties of selected His-tagged derivatives of pi (His-pi x wt and three hyperactive replication variants) to determine if the functionality of these proteins in replication, DNA binding, and oligomerization is altered. Our results indicate that these tagged proteins retain the characteristics previously demonstrated for their non-tagged counterparts making them suitable for ongoing studies of pi protein structure and functions in replication and transcription.