3-DIMENSIONAL STRUCTURE IN SOLUTION OF A WHEAT LIPID-TRANSFER PROTEINFROM MULTIDIMENSIONAL H-1-NMR DATA - A NEW FOLDING FOR LIPID CARRIERS

Two-dimensional and three-dimensional H-1-NMR experimental data [Simor re, J. P., Caille, A., Marion, D., Marion, D. and Ptak, M. (1991) Bioc hemistry 30, 11600-11608] were used to build models of the three-dimen sional structure of a non-specific wheat lipid-transfer protein (LTP) by using distance geometry, simulated annealing, energy minimization a nd molecular dynamics techniques. A first set of 881 distance constrai nts derived from NOE cross-peak intensities was used to generate 74 in itial structures. One family of topological mirror images of the prote in structure was eliminated by considering helical secondary-structure organization and steric requirements. Back calculations of NOE intens ities led us to introduce 535 additional distance constraints. Finally , 21 structures were selected as representative of the structure of th e protein. The polypeptide backbone folds into a simple and original r ight-handed winding. It is composed of a bundle of four helices linked by flexible loops, which is packed against a C-terminal fragment form ing a non-standard saxophone-like shape. The folded protein is stabili zed by hydrophobic interactions and the four disulfide bridges combine d by pairs on each side of the protein. An hydrophobic cleft, formed b y residues located in the second half of the protein could be a potent ial site for the binding of lipids.