Structure of the Enterococcus faecalis EIIA gnt PTS component

Abstract

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 EIIA gnt component of the so far little investigated Enterococcus faecalis gluconate specific PTS. The crystal structure shows a tightly interacting dimer of EIIA gnt which is structurally similar to the related EIIA man from Escherichia coli. Homology modeling of E. faecalis HPr, EIIB man and their complexes with EIIA man suggests that despite moderate sequence identity between EIIA man and EIIA gnt, the active sites closely match the situation observed in the E. coli system with His-9 of EIIA gnt being the likely phosphoryl group carrier. We therefore propose that the phosphoryl transfer reactions involving EIIA gnt proceed according to a mechanism analog to the one described for E. coli EIIA man.