title: Interresidual distance determination by four-pulse double electron-electron resonance in an integral membrane protein: the Na+/proline transporter PutP of Escherichia coli.
abstract: Proximity relationships within three doubly spin-labeled variants of the Na+/proline transporter PutP of Escherichia coli were studied by means of four-pulse double electron-electron resonance spectroscopy. The large value of 4.8 nm for the interspin distance determined between positions 107 in loop 4 and 223 in loop 7 strongly supports the idea of these positions being located on opposite sides of the membrane. Significant smaller values of between 1.8 and 2.5 nm were found for the average interspin distances between spin labels attached to the cytoplasmic loops 2 and 4 (position 37 and 107) and loops 2 and 6 (position 37 and 187). The large distance distribution widths visible in the pair correlation functions reveal a high flexibility of the studied loop regions. An increase of the distance between positions 37 and 187 upon Na+ binding suggests ligand-induced structural alterations of PutP. The results demonstrate that four-pulse double electron-electron resonance spectroscopy is a powerful means to investigate the structure and conformational changes of integral membrane proteins reconstituted in proteoliposomes.
authors.affiliation: Max-Planck-Institut für Polymerforschung, 55128 Mainz, Germany.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Jeschke
authors.forename: Christoph
authors.initials: C
authors.lastname: Wegener
authors.forename: Monika
authors.initials: M
authors.lastname: Nietschke
authors.forename: Heinrich
authors.initials: H
authors.lastname: Jung
authors.forename: Heinz-Jürgen
authors.initials: HJ
authors.lastname: Steinhoff
mesh_terms: D026921:Amino Acid Transport Systems, Neutral / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004926:Escherichia coli / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D013113:Spin Labels; D013223:Statistics as Topic
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D008565:Membrane Proteins; D013113:Spin Labels; C033082:proline transporter