Improving the glycosyltransferase activity of Agrobacterium tumefaciens glycogen synthase by fusion of N-terminal starch binding domains (SBDs)

To further investigate the functional role of A. thaliana SSIII-SD, three chimeric proteins were constructed combining the SBDs from A. thaliana with the GS from A. tumefaciens. Recombinant proteins were expressed in and purified to homogeneity from Escherichia coli cells in order to be kinetically characterized. Furthermore, we tested the ability to restore in vivo glycogen biosynthesis in transformed E. coli glgA− cells, deficient in GS. Results show that the D3-GS chimeric enzyme showed increased capacity of glycogen synthesis in vivo with minor changes in its kinetics parameters compared to GS.