title: 1H-15N-NMR studies of bacteriorhodopsin Halobacterium halobium. Conformational dynamics of the four-helical bundle.
abstract: Series of uniformly and selectively 15N-labeled bacteriorhodopsins of Halobacterium halobium (strain ET 1001) were obtained and a 1H-15N-NMR study was performed in methanol/chloroform (1:1) and 0.1 M NH4CHOO, medium which mimics that in the membrane in vivo. Less than half of the cross-peaks expected from the amino acid sequence of uniformly 15N-labeled bacteriorhodopsin were observed, using heteronuclear 1H-15N coherence spectroscopy. In order to assign the observed cross-peaks, a selective 15N-labeling of amino acid residues (Tyr, Phe, Trp, Lys, Gly, Leu, Val or Ile) was carried out and 1H-15N-NMR spectra of bacteriorhodopsin and its fragments C1 (residues (72-231), C2 (residues 1-71), B1 (residues 1-155) and BP2 (residues 163-231) were investigated. By this procedure, all observed 1H-15N cross-peaks of the entire bacteriorhodopsin were found to belong to the transmembrane segments A, B and G. The cross-peaks from four (C, D, E and F) helical bundles (79-189 residues) were missed. These results clearly indicate that dynamic processes occur in the four helice bundle. The significance of this, in respect to bacteriorhodopsin functioning, is discussed.
authors.affiliation: Shemyakin Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow.
authors.lastname: Orekhov VYu
authors.forename: G V
authors.initials: GV
authors.lastname: Abdulaeva
authors.lastname: Musina LYu
authors.forename: A S
authors.initials: AS
authors.lastname: Arseniev
mesh_terms: D000595:Amino Acid Sequence; D001436:Bacteriorhodopsins / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry; D019617:Halobacterium salinarum / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D017433:Protein Structure, Secondary; D011522:Protons
chemical_list: D009587:Nitrogen Isotopes; D011522:Protons; D001436:Bacteriorhodopsins