The dual-function glutamate transporters: structure and molecular characterisation of the substrate-binding sites

AbstractGlutamate transporters are essential for terminating synaptic excitation and for maintaining extracellular glutamate concentrations below neurotoxic levels. These transporters also mediate a thermodynamically uncoupled chloride flux, activated by two of the molecules they transport, sodium and glutamate. Five eukaryotic glutamate transporters have been cloned and identified. They exhibit ∼50% identity and this homology is even greater at the carboxyl terminal half, which is predicted to have an unusual topology. Determination of the topology shows that the carboxyl terminal part contains several transmembrane domains separated by two reentrant loops that are in close proximity to each other. We have identified several conserved amino acid residues in the carboxyl terminal half that play crucial roles in the interaction of the transporter with its substrates: sodium, potassium and glutamate. The conformation of the transporter gating the anion conductance is different from that during substrate translocation. However, there exists a dynamic equilibrium between these conformations

Surface structure of MX-chains studied by atomic force microscopy

The surfaces of mixed-valence halogen-bridged transition metal linear chain compounds [[Pt(en){sub 2}][Pt(en)]{sub 2}(X{sub 1-y}X{prime}{sub y}){sub 2}](ClO{sub 4}){sub 4} (X, X{prime} = Cl, Br, or I; en = C{sub 2}H{sub 8}N{sub 2}; y = 0.0 - 1.0) were examined by atomic force microscopy (AFM). The AFM images are consistent with the surfaces expected from the bulk crystal structure. The surface unit cell parameters of the images correspond to the lattice constants of the bulk crystals. The patterns of the atomic-scale AFM images are dominated by the most protruded H atoms of the en ligands and the most protruded O atoms of the ClO{sub 4}{sup -} anions