Structure of the Enterococcus faecalis EIIAgnt PTS component

In Eubacteria, the utilization of a number of extracellular carbohydrates is mediated by sugar specific phosphoenolepyruvate (PEP) dependent sugar phosphotransferase systems (PTSs), which simultaneously import und phosphorylate their target sugars. Here, we report the crystal structure of the EIIAgnt component of the so far little investigated Enterococcus faecalis gluconate specific PTS. The crystal structure shows a tightly interacting dimer of EIIAgnt which is structurally similar to the related EIIAman from Escherichia coli. Homology modeling of E. faecalis HPr, EIIBman and their complexes with EIIAman suggests that despite moderate sequence identity between EIIAman and EIIAgnt, the active sites closely match the situation observed in the E. coli system with His-9 of EIIAgnt being the likely phosphoryl group carrier. We therefore propose that the phosphoryl transfer reactions involving EIIAgnt proceed according to a mechanism analog to the one described for E. coli EIIAman.