1H NMR and fluorescence studies of the complexation of DMPG by wheat non-specific lipid transfer protein. Global fold of the complex.

Plant non-specific lipid transfer proteins (LTPs) are proteins which transfer lipids between membranes in vitro and are believed to be involved in the transport of cutin monomers to the cuticle layer in vivo or in the plant defence against phytopathogens. The complexation of DMPG, a diacyl phospholipid, by wheat ns-LTP, a protein extracted from wheat seeds, was followed by 1H NMR and fluorescence spectroscopy. The global fold of the protein was calculated using the DIANA software package from a list of 968 distance constraints. The internal cavity volume, a feature common to all known ns-LTP structures, was estimated to be 750 A3 using the 'CAVITE' program. This model of the complex was obtained by inserting a lipid molecule in the cavity and was energy minimized. The study showed that the protein fold described for the free form was only weakly affected by the insertion of the bulky lipid. Observation of some intermolecular NOEs between the protein and the lipid glycerol moiety revealed that the cavity entrance was located between residues His35 and Arg44. The resulting solution structure was compared to the crystal structure of the maize ns-LTP/palmitate complex.