Atomistic insight into the luminal allosteric regulation of vesicular glutamate transporter 2 by chloride and...

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^- .