Abstract
The bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes as well as effecting sugar transport. The crr gene product (enzyme IIA(Glc) (IIA(Glc))) mediates some of these regulatory phenomena. In this report, we characterize a novel IIA(Glc)-binding protein from Escherichia coli extracts, discovered using ligand-fishing with surface plasmon resonance spectroscopy. This protein, which we named FrsA (fermentation/respiration switch protein), is the 47-kDa product of the yafA gene, previously denoted as "function unknown." FrsA forms a 1:1 complex specifically with the unphosphorylated form of IIA(Glc), with the highest affinity of any protein thus far shown to interact with IIA(Glc). Orthologs of FrsA have been found to exist only in facultative anaerobes belonging to the gamma-proteobacterial group. Disruption of frsA increased cellular respiration on several sugars including glucose, while increased FrsA expression resulted in an increased fermentation rate on these sugars with the concomitant accumulation of mixed-acid fermentation products. These results suggest that IIA(Glc) regulates the flux between respiration and fermentation pathways by sensing the available sugar species via a phosphorylation state-dependent interaction with FrsA.
Highlights
The bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes as well as effecting sugar transport
In our previous study, employing ligand-fishing in E. coli extracts with surface plasmon resonance spectroscopy and immobilized HPr as the bait, we discovered a high affinity binding of glycogen phosphorylase to HPr; HPr mediates cross-talk between sugar uptake through the phosphotransferase system (PTS) and glycogen breakdown (8 –10)
Each protein component of the E. coli PTS involved in glucose uptake has been shown to regulate the activity of a partner protein by a direct protein-protein interaction
Summary
The bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes as well as effecting sugar transport. These results suggest that IIAGlc regulates the flux between respiration and fermentation pathways by sensing the available sugar species via a phosphorylation state-dependent interaction with FrsA.
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