title: Time-resolved detection of structural changes during the photocycle of spin-labeled bacteriorhodopsin.
abstract: Bacteriorhodopsin was selectively spin labeled at residues 72, 101, or 105 after replacement of the native amino acids by cysteine. Only the electron paramagnetic resonance spectrum of the label at 101 was time-dependent during the photocycle. The spectral change rose with the decay of the M intermediate and fell with recovery of the ground state. The transient signal is interpreted as the result of movement in the C-D or E-F interhelical loop, or in both, coincident with protonation changes at the key aspartate 96 residue. These results link the optically characterized intermediates with localized conformational changes in bacteriorhodopsin during the photocycle.
authors.affiliation: Institut für Biophysik, Ruhr-Universität Bochum, Germany.
authors.forename: H J
authors.initials: HJ
authors.lastname: Steinhoff
authors.forename: R
authors.initials: R
authors.lastname: Mollaaghababa
authors.forename: C
authors.initials: C
authors.lastname: Altenbach
authors.forename: K
authors.initials: K
authors.lastname: Hideg
authors.forename: M
authors.initials: M
authors.lastname: Krebs
authors.forename: H G
authors.initials: HG
authors.lastname: Khorana
authors.forename: W L
authors.initials: WL
authors.lastname: Hubbell
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D008027:Light; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013113:Spin Labels
chemical_list: D013113:Spin Labels; D001436:Bacteriorhodopsins