Abstract
Plant lipid transfer proteins (LTPs) are small, basic proteins able to transport phospholipids between membranes. They are abundant in plants and are found to have specific expression patterns and functions in different tissues. The structures of LTPs of several plants have been solved either by X-ray or by NMR. All of them show a similar conformation of a single, compact domain stabilized by 4 conserved-disulfide bonds. A characteristic of these structures is that they bear a hydrophobic cavity running through the molecule, which has been proven to be the ligand-binding site. Despite of their function of phospholipid-transportation, the LTP/phospholipid complex has never been isolated. However, strong binding has been found between LTPs and fatty acids. In this study we used a novel fluorescence dye, 1-anilino-8-naphthalene sulfonic acid (ANS), to measure the binding affinities of different fatty acids to rice LTP, and compared them with the stability of fatty acid/LTP complexes measured by circular dichroism (CD). The results showed that fatty acids with better affinities to LTP helps in stabilizing the structure of LTP, and that the affinities of fatty acids to LTP are strongly related to their chain lengths. The binding between rice LTP and ANS was confirmed by NMR spectroscopy. Kinetic studies of the binding reaction between myristic acid (MA) and rice LTP was carried out on the biosensor, BIAcore2000. The results confirmed that the reaction was a 1:1 binding.