Computational Approaches to Understanding the Mechanism of Transport in the Na+/Galactose Co-Transporter vSGLT


A number of recent high resolution structures suggest that a larger family of cation coupled substrate transporters share a common core architecture. At the molecular level, it is not known how this architecture enables them to harness the energy stored in ionic gradients to move small molecules across the membrane. We have studied the details of substrate and ion entry and exit to the cytoplasm of the galactose symporter vSGLT. We used equilibrium molecular dynamics (MD) simulations to determine the role of key residues in stabilizing galactose and sodium in their respective binding sites. The simulations show that the transporter is stable when simulated as a monomer having only small deviations from the x-ray structure. We also used steered MD simulations to pull galactose and sodium from their site into the cytoplasm to obtain the free energy for unbinding.

Biophys. J.