Structural basis of a GatC ortholog transporter in the bacterial phosphotransferase system

The bacterial phosphotransferase system (PTS) mediates the uptake of specific carbohydrates via IIC transporters. Here, we report the crystal and cryo-electron microscopy (cryo-EM) structures of Leminorella grimontii galactitol-specific PTS enzyme IIC component (LgGatC), which is implicated in D-xylose uptake and belongs to the ascorbate–galactitol (AG) superfamily of IIC proteins. These structures, determined in the presence and absence of D-xylose, capture the transporter in an outward-facing conformation. A homology model of an inward-facing state, constructed based on these structures, supports an elevator-like transport mechanism. These findings provide structural insights into substrate recognition by GatC and offer a framework for understanding sugar transport in PTS IIC proteins.