title: Probing the hydrophobic cavity of lipid transfer protein from Nicotiana tabacum through xenon-based NMR spectroscopy.
abstract: The hydrophobic cavity of Lipid Transfer Protein 1 from Nicotiana tabacum is investigated in detail by NMR using xenon as a spy. The analysis of the (129)Xe chemical shifts and self-relaxation times gives evidence of protein-xenon interaction. Thermodynamics of the binding is characterized through the study of aliphatic (1)H and (13)C chemical shift variation as a function of xenon pressure. The binding constant is evaluated to 75.5 +/- 1.0 M(-1) at 293 K. The location of xenon inside the cavity is deduced from SPINOE experiments. The noble gas appears to occupy four sites, and xenon self-relaxation experiments indicate that it quickly jumps between different sites. The chemical shifts of amide protons and nitrogens also depend on the xenon concentration, either specifically or nonspecifically for atoms at the external surface of the protein. Yet, contrary to aliphatic atoms, they do not correspond to short-range interactions as confirmed by magnetization transfer experiments between laser-polarized xenon and protons in H(2)O. These (15)N chemical shift variations, used in combination with (15)N transverse self-relaxation rates to determine the lower limit of the binding rate, consequently reveal subtle changes in the structure of the protein upon binding.
authors.affiliation: DSM/DRECAM/Service de Chimie Moléculaire, URA CEA/CNRS 331 Claude Fréjacques, C.E.A./Saclay, F-91191 Gif sur Yvette, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Dubois
authors.forename: Pedro
authors.initials: P
authors.lastname: Da Silva
authors.forename: Céline
authors.initials: C
authors.lastname: Landon
authors.forename: J Gaspard
authors.initials: JG
authors.lastname: Huber
authors.forename: Michel
authors.initials: M
authors.lastname: Ponchet
authors.forename: Françoise
authors.initials: F
authors.lastname: Vovelle
authors.forename: Patrick
authors.initials: P
authors.lastname: Berthault
authors.forename: Hervé
authors.initials: H
authors.lastname: Desvaux
mesh_terms: D052179:Antigens, Plant; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D003198:Computer Simulation; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D012996:Solutions; D013816:Thermodynamics; D014026:Nicotiana / Q000378:metabolism*; D014978:Xenon
chemical_list: D052179:Antigens, Plant; D002352:Carrier Proteins; D010940:Plant Proteins; D012996:Solutions; C511920:lipid transfer proteins, plant; D014978:Xenon