Atomistic insight into the luminal allosteric regulation of vesicular glutamate transporter 2 by chloride and protons: An all-atom molecular dynamics simulation study.

Vesicular glutamate transporters (VGLUTs) are essential components of synaptic transmission in the brain. Synaptic vesicles' luminal chloride and low pH regulate VGLUTs allosterically in a cooperative way. The luminal allosteric regulation of VGLUTs by chloride (Cl ) and proton (H ) is possible through the collective work of luminal Cl and H binding site residues. However, precise atomistic details about the luminal Cl binding to the luminal Cl binding site and the role of allosteric activation by H in VGLUTs are unknown. Using all-atom molecular dynamics simulations, this study demonstrates the critical role of Cl binding site residues, details about Cl binding to the luminal Cl binding site, and the role of allosteric regulation of VGLUT2 by H at an atomistic level. By point mutations, we found out that Arginine (R184), Histidine (H128), and Glutamate (E191) are critical residues in the allosteric regulation of VGLUT2, R184 is the luminal Cl binding site residue, and H128 and R88 support Cl binding to R184. Furthermore, we found out that the protonation of H128 and E191 is important in Cl binding to the luminal Cl binding site. Furthermore, we investigated the essential interactions between Cl and H binding site residues. Our results can give atomistic evidence for a previous experimental hypothesis about the VGLUTs luminal allosteric regulation by H and Cl .