title: Conformational heterogeneity of the aspartate transporter Glt(Ph).
abstract: Glt(Ph) is a Pyrococcus horikoshii homotrimeric Na(+)-coupled aspartate transporter that belongs to the glutamate transporter family. Each protomer consists of a trimerization domain involved in subunit interaction and a transporting domain with the substrate-binding site. Here, we have studied the conformational changes underlying transport by Glt(Ph) using EPR spectroscopy. The trimerization domains form a rigid scaffold, whereas the transporting domains sample multiple conformations, consistent with large-scale movements during the transport cycle. Binding of substrates changed the occupancies of the different conformational states, but the domains remained heterogeneous. The membrane environment favored conformations different from those observed in detergent micelles, but the transporting domain remained structurally heterogeneous in both environments. We conclude that the transporting domains sample multiple conformational states with substantial occupancy regardless of the presence of substrate and coupling ions, consistent with equilibrium constants close to unity between the observed transporter conformations.
authors: Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
authors: Inga
authors: I
authors: Hänelt
authors: Dorith
authors: D
authors: Wunnicke
authors: Enrica
authors: E
authors: Bordignon
authors: Heinz-Jürgen
authors: HJ
authors: Steinhoff
authors: Dirk Jan
authors: DJ
authors: Slotboom
mesh_terms: D026922:Amino Acid Transport Systems, Acidic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D016296:Mutagenesis; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry; D043902:Pyrococcus horikoshii / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D026922:Amino Acid Transport Systems, Acidic; D019843:Archaeal Proteins; D021122:Protein Subunits; D001224:Aspartic Acid; D012964:Sodium