Structural and Functional Underpinnings of Proton Coupling in Glutamate Transporters

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PROJECT ABSTRACT Glutamate is the primary excitatory neurotransmitter in the brain and is necessary for several crucial brain functions. Mammalian glutamate transporters, or excitatory amino acid transporters (EAATs), are responsible for rapidly clearing excessive glutamate to prevent excitotoxicity and in shaping synaptic transmission. Therefore, EAATs dysfunction is often linked to neurological pathologies. Most of our understanding resulted from studying archaeal homologue, GltPh from Pyrococcus horikoshii. In EAATs, substrate transport is coupled to three sodiums, one proton, and the countertransport of a potassium ion, while GltPh is exclusively sodium-coupled, so there is limited insight as to how protons bind, and the mechanism by which they drive transport. Bacterial homologue, GltTBc from Bacillus caldotenax, is driven by symport of protons rather than sodium ions. These homologues share a similar trimeric structure but have different ion-coupling specificity. There is no high-resolution structure for GltTBc or any other proton-coupled transporter of this family. The goal of my first Aim is to obtain a high-resolution structure of GltTBc to both identify potential protonation sites and understand the structural basis of specificity during ion coupling. To determine the role of protons during substrate transport in GltTBc, Aim 2 will elucidate whether protons drive glutamate binding or translocation and understand the molecular basis of proton coupling. Under this fellowship, I will have access to consult with leading researchers from Weill Cornell and associated core research facilities. Being in the middle of the “corridor of science”, which is composed of Weill Cornell, The Rockefeller Institution, and Memorial Sloan Kettering Cancer Center, will provide me with ample opportunities and resources to not only enhance my technical skills, but allow me to present and communicate my work to the scientific community. This will be aided by my PI’s recent advancements in establishing the Molecular Biophysics Training Program, which provides another source of support, community, and expertise within the Tri-Institiutional campus.