MhLap Dextran Binding

The first step in assessing the feasibility of using dextran to crosslink M. hydrocarbonoclasticus to our biofilm was to test the ability of this bacterium’s sugar binding domain to bind dextran. Luckily, Tyler Vance of Dr. Davies’ lab already had the sugar-binding MhLap Region III cloned into pET-28 for overexpression in E. coli. We expressed, then purified this construct using a Ni-NTA column. Purified MhLap Region III fractions were pooled. We then set up a simple affinity chromatography binding assay. A Pasteur pipette was filled half-way with sephadex G-200 slurry. Purified MhLap was then added, followed by five washes with buffer. We then washed twice with 5 mg/mL dextran solution. Finally, the column was washed twice with EDTA to nonspecifically elute all protein. The collected fractions can be seen in the following SDS gels. A significant amount of protein was eluted by dextran, shown by the MhLap band in the D2 lane. The dextran solution added would act as a competitor for Sephadex binding. This suggests MhLap does indeed bind dextran. The large band eluted by EDTA in E2 is also MhLap. This suggests MhLap binding to the Sephadex solid phase is strong enough that aqueous dextran is insufficient for full elution.