title: Protein stability and plasticity of the hydrophobic cavity in wheat ns-LTP.
abstract: Plant ns-LTPs display an original structure with four helices and a flexible C-terminus, maintained together by four disulphide bridges and delineating an elongated central hydrophobic cavity. In order to relate these structural features to the protein stability and plasticity, combined molecular mechanics and simulated annealing calculations were undertaken on a wheat ns-LTP "mutant" with Cys-Ala replacement and with the application of core inter-residue restraints up to 2 A, reducing the cross-section size of the hydrophobic cavity. Analysis of the energy-minimized structures shows that removal of the disulphide bridges results in structures with a lower total energy and a smaller cavity volume. A 1-ns MD simulation at 300K in water, underlines that, despite the absence of a well-packed hydrophobic core, the native structure is extremely stable at room temperature and the cavity is not hydrated. This confirms that the disulphide bridges are essential for the existence of the cavity, whereas its plasticity depends both on the hydrophobic chain lining the cavity and on the C-terminal flexibility. A high temperature (500K) MD simulation confirms the stability of the secondary structure elements and the flexibility of the loops and of the C-terminal segment. Two important structural transitions during this simulation are discussed and possible routes for the insertion and release of hydrophobic ligands are suggested.
authors.affiliation: Centre de Biophysique Moléculaire CNRS, Orléans University, rue Charles-Sadron, F-45071 Orleans cedex 2, France. sy@cnrs-orleans.fr
authors.forename: Denise
authors.initials: D
authors.lastname: Sy
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Gravier
authors.forename: Julia
authors.initials: J
authors.lastname: Goodfellow
authors.forename: Fraçoise
authors.initials: F
authors.lastname: Vovelle
mesh_terms: D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D052179:Antigens, Plant; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013696:Temperature; D014908:Triticum / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D052179:Antigens, Plant; D002352:Carrier Proteins; D004220:Disulfides; D008024:Ligands; D010940:Plant Proteins; C511920:lipid transfer proteins, plant; D014867:Water; D003545:Cysteine; D000409:Alanine