Crystal structure of an asymmetric trimer of a bacterial glutamate transporter homolog

We report a structure of a trimeric glutamate transporter homolog from Pyrococcus horikoshii with two protomers in an inward facing state and the third in an intermediate conformation between the outward and inward facing states. The intermediate shows a cavity in the thinnest region of the transporter, which is potentially accessible to extracellular and cytoplasmic solutions. Our findings suggest a structural principle by which transport intermediates may mediate uncoupled permeation of polar solutes.

[1]  R. Vandenberg,et al.  Slips, leaks and channels in glutamate transporters , 2008, Channels.

[2]  S. Amara,et al.  Arachidonic acid elicits a substrate-gated proton current associated with the glutamate transporter EAAT4 , 1998, Nature Neuroscience.

[3]  J. Mindell,et al.  The uncoupled chloride conductance of a bacterial glutamate transporter homolog , 2007, Nature Structural &Molecular Biology.

[4]  S. Amara,et al.  Sulfhydryl modification of V449C in the glutamate transporter EAAT1 abolishes substrate transport but not the substrate-gated anion conductance , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[5]  M. Kavanaugh,et al.  Differential Modulation of Human Glutamate Transporter Subtypes by Arachidonic Acid (*) , 1995, The Journal of Biological Chemistry.

[6]  R. Vandenberg,et al.  Distinct Conformational States Mediate the Transport and Anion Channel Properties of the Glutamate Transporter EAAT-1* , 2002, The Journal of Biological Chemistry.

[7]  R. Vandenberg,et al.  Niflumic acid modulates uncoupled substrate‐gated conductances in the human glutamate transporter EAAT4 , 2001, The Journal of physiology.

[8]  B. Kanner,et al.  Coupled, but Not Uncoupled, Fluxes in a Neuronal Glutamate Transporter Can Be Activated by Lithium Ions* , 2001, The Journal of Biological Chemistry.

[9]  M. Kavanaugh,et al.  Dynamic Equilibrium between Coupled and Uncoupled Modes of a Neuronal Glutamate Transporter* , 2002, The Journal of Biological Chemistry.

[10]  K. Shimamoto,et al.  Sulfhydryl modification of cysteine mutants of a neuronal glutamate transporter reveals an inverse relationship between sodium dependent conformational changes and the glutamate-gated anion conductance , 2005, Neuropharmacology.

[11]  E. Hartveit,et al.  Activation of a presynaptic glutamate transporter regulates synaptic transmission through electrical signaling , 2006, Nature Neuroscience.

[12]  M. Kavanaugh,et al.  An excitatory amino-acid transporter with properties of a ligand-gated chloride channel , 1995, Nature.

[13]  R. Vandenberg,et al.  The Chloride Permeation Pathway of a Glutamate Transporter and Its Proximity to the Glutamate Translocation Pathway* , 2004, Journal of Biological Chemistry.

[14]  M. Kavanaugh,et al.  Kinetics of a human glutamate transporter , 1995, Neuron.

[15]  M. Kavanaugh,et al.  Excitatory amino acid transporter 5, a retinal glutamate transporter coupled to a chloride conductance. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[16]  E. Gouaux,et al.  Structure of a glutamate transporter homologue from Pyrococcus horikoshii , 2004, Nature.

[17]  R. Vandenberg,et al.  Mutations in transmembrane domains 5 and 7 of the human excitatory amino acid transporter 1 affect the substrate-activated anion channel. , 2007, Biochemistry.

[18]  Eric Gouaux,et al.  Coupling substrate and ion binding to extracellular gate of a sodium-dependent aspartate transporter , 2007, Nature.

[19]  N. Reyes,et al.  Transport mechanism of a bacterial homologue of glutamate transporters , 2009, Nature.